Key Financial Data Of Reporting Company
| Concept | As at 2024-03-31 | 2023-04-01 to 2024-03-31 | As at 2024-03-31 | 2023-04-01 to 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | 2022-04-01 to 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | 2022-04-01 to 2023-03-31 | 2021-04-01 to 2022-03-31 | 2021-04-01 to 2022-03-31 | As at 2022-03-31 | As at 2022-03-31 | As at 2021-03-31 | 2020-04-01 to 2021-03-31 | 2020-04-01 to 2021-03-31 | As at 2021-03-31 | 2019-04-01 to 2020-03-31 | As at 2020-03-31 | 2019-04-01 to 2020-03-31 | As at 2020-03-31 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Key financial data of reporting company | ||||||||||||||||||||||
| Business results of reporting company | ||||||||||||||||||||||
| Net sales | — | 
                                                4,852,954,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                6,661,561,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                6,661,561,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                7,354,847,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                7,432,884,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                6,620,076,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,649,521,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                6,567,071,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                6,614,552,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Ordinary profit (loss) | — | 
                                                -482,079,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -112,231,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -93,232,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                272,062,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                267,925,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                266,543,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                220,688,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                227,139,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                176,938,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) | — | 
                                                -599,743,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -158,352,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                161,806,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                182,326,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                150,079,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Equity in earnings (losses) of affiliates if equity method is applied | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Share capital | — | — | — | — | — | 
                                                156,100,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                156,100,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                156,100,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                156,100,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                156,100,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total number of issued shares | — | — | — | — | — | 
                                                5,500,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
                                                5,500,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | — | — | 
                                                5,500,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | 
                                                5,500,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | 
                                                5,500,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
| Net assets | — | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,449,216,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,271,682,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,271,640,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                4,639,506,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,660,475,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,634,829,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                4,744,778,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,643,482,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,715,034,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | — | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,953,904,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                7,940,864,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                7,940,825,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                8,713,210,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                8,733,404,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                8,138,653,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                8,218,131,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                7,431,294,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                7,483,572,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets per share | — | — | — | — |  | 
                                                633.05
                                                
                                             | — | 
                                                784.00
                                                
                                             | 
                                                783.98
                                                
                                             | — | — | — | 
                                                851.50
                                                
                                             | 
                                                855.36
                                                
                                             | 
                                                850.64
                                                
                                             | — | — | 
                                                870.83
                                                
                                             | — | 
                                                852.21
                                                
                                             | — | 
                                                865.36
                                                
                                             | 
| Dividend paid per share | — | 
                                                41
                                                
                                             | — | — | — | — | 
                                                41
                                                
                                             | — | — | — | 
                                                41
                                                
                                             | — | — | — | — | 
                                                41
                                                
                                             | — | — | 
                                                39
                                                
                                             | — | — | — | 
| Interim dividend paid per share | — | 
                                                20
                                                
                                             | — | — | — | — | 
                                                20
                                                
                                             | — | — | — | 
                                                20
                                                
                                             | — | — | — | — | 
                                                20
                                                
                                             | — | — | 
                                                19
                                                
                                             | — | — | — | 
| Basic earnings (loss) per share | — | 
                                                -110.07
                                                
                                             | — |  | — | — | 
                                                -29.06
                                                
                                             | — | — | 
                                                -24.58
                                                
                                             | 
                                                29.69
                                                
                                             | 
                                                45.67
                                                
                                             | — | — | — | 
                                                33.46
                                                
                                             | 
                                                25.02
                                                
                                             | — | 
                                                27.54
                                                
                                             | — | 
                                                18.43
                                                
                                             | — | 
| Diluted earnings per share | — |  | — |  | — | — |  | — | — |  |  |  | — | — | — |  |  | — |  | — |  | — | 
| Equity-to-asset ratio | — | — | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.496
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.538
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.538
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.532
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.534
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.569
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.577
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.625
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.630
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Rate of return on equity | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.034
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.054
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.039
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.029
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.031
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.021
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Price-earnings ratio | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                27.4
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                17.8
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                26.6
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                35.6
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                29.0
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                43.4
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Payout ratio | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.381
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                1.225
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                1.416
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
| Net cash provided by (used in) operating activities | — | 
                                                313,066,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                276,453,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -51,628,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,140,862,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                390,388,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) investing activities | — | 
                                                719,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -150,564,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -1,179,210,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -163,119,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -512,404,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) financing activities | — | 
                                                -268,136,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -323,432,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                398,528,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -188,708,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                175,429,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | — | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                402,831,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                444,113,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                636,690,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,461,114,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                671,945,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Number of employees | 
                                                25
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                195
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                220
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                240
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                240
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                242
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                242
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                255
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                244
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                254
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                242
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                15
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                20
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                36
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                36
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                36
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                36
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                32
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                32
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                35
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                35
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total shareholder return | — | — | — | — | — | 
                                                1.301
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.204
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1.168
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.213
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.049
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total return on share price index | — | — | — | — | — | 
                                                1.962
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.388
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1.312
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.286
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.905
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             |