Key Financial Data Of Reporting Company
| Concept | As at 2025-03-31 | As at 2025-03-31 | 2024-04-01 to 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2024-03-31 | 2023-04-01 to 2024-03-31 | As at 2023-03-31 | 2022-04-01 to 2023-03-31 | 2021-04-01 to 2022-03-31 | As at 2022-03-31 | 2020-04-01 to 2021-03-31 | As at 2021-03-31 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Key financial data of reporting company | |||||||||||||
| Business results of reporting company | |||||||||||||
| Net sales | — | — | 
                                                60,563,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                55,407,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                51,015,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                49,632,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                49,251,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Ordinary profit (loss) | — | — | 
                                                3,780,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,868,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,215,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,996,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,227,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) | — | — | 
                                                -3,288,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,377,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,605,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,483,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,607,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Equity in earnings (losses) of affiliates if equity method is applied | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Share capital | — | — | — | — | 
                                                10,758,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                10,758,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                10,758,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                10,758,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                10,758,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total number of issued shares | — | — | — | — | 
                                                9,451,169
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                9,451,169
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
                                                9,451,169
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | 
                                                9,451,169
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
                                                9,451,169
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
| Net assets | — | — | — | — | 
                                                33,043,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                36,661,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                35,649,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                34,532,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                33,683,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | — | — | — | — | 
                                                81,729,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                75,802,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                72,466,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                69,334,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                69,876,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets per share | — | — | — | — | 
                                                3,869.10
                                                
                                             | 
                                                4,290.55
                                                
                                             | — | 
                                                4,064.76
                                                
                                             | — | — | 
                                                3,936.70
                                                
                                             | — | 
                                                3,839.54
                                                
                                             | 
| Dividend paid per share | — | — | 
                                                82.00
                                                
                                             | — | — | — | 
                                                70.00
                                                
                                             | — | 
                                                70.00
                                                
                                             | 
                                                60.00
                                                
                                             | — | 
                                                60.00
                                                
                                             | — | 
| Interim dividend paid per share | — | — | 
                                                40.00
                                                
                                             | — | — | — | 
                                                35.00
                                                
                                             | — | 
                                                30.00
                                                
                                             | 
                                                30.00
                                                
                                             | — | 
                                                30.00
                                                
                                             | — | 
| Basic earnings (loss) per share | — | — | 
                                                -384.95
                                                
                                             | — | — | — | 
                                                159.98
                                                
                                             | — | 
                                                183.07
                                                
                                             | 
                                                169.09
                                                
                                             | — | 
                                                183.18
                                                
                                             | — | 
| Diluted earnings per share | — | — |  | — | — | — |  | — |  |  | — |  | — | 
| Equity-to-asset ratio | — | — | — | — | 
                                                0.404
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.484
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.492
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.498
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.482
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Rate of return on equity | — | — | 
                                                -0.094
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.038
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.046
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.043
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.049
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Price-earnings ratio | — | — | 
                                                -6.3
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                13.8
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                10.9
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                12.9
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                13.9
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Payout ratio | — | — | 
                                                -0.213
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.438
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.382
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.355
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.328
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) operating activities | — | — | 
                                                -3,305,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                627,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,853,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,498,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,230,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) investing activities | — | — | 
                                                -3,168,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -3,536,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -1,373,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -1,553,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -978,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) financing activities | — | — | 
                                                7,618,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                14,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -813,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -1,671,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -2,446,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | — | — | — | — | 
                                                6,264,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,120,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                8,014,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                7,347,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                7,074,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Number of employees | 
                                                1,279
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                60
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,340
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,307
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1,314
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                1,344
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1,356
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total shareholder return | — | — | — | — | 
                                                1.330
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1.176
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.044
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                1.102
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.245
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total return on share price index | — | — | — | — | 
                                                2.134
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                2.168
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.534
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                1.450
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.421
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             |