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 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 | 2023-04-01 to 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 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Key financial data of reporting company | ||||||||||||||||||||||||||
| Business results of reporting company | ||||||||||||||||||||||||||
| Net sales | — | — | 
                                                11,259,429,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                5,606,685,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                7,211,577,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                12,248,450,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                6,508,701,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                10,919,983,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,261,243,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                10,472,199,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                6,907,561,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                10,983,007,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Ordinary profit (loss) | — | — | 
                                                -476,322,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -528,663,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                201,724,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                323,431,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                189,496,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                268,023,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                165,963,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                220,889,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                217,919,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                258,140,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) | — | — | — | — | — | — | — | 
                                                -317,703,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                231,617,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                234,440,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                202,082,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                275,279,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Share capital | — | — | — | 
                                                738,599,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                738,599,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                738,599,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                738,599,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                738,599,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total number of issued shares | — | — | — | 
                                                1,392,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                1,392,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
                                                1,392,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1,392,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | 
                                                1,392,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
| Net assets | — | 
                                                5,019,990,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,412,483,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
                                                6,153,927,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,528,191,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,476,705,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,016,340,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                5,745,279,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,304,274,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,203,046,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                5,799,189,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | — | 
                                                12,966,663,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                9,498,819,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
                                                15,204,750,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                11,551,669,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                10,979,144,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                13,944,091,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                13,619,035,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                10,755,176,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                14,561,620,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                11,641,414,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets per share | — | 
                                                3,041.96
                                                
                                             | — | 
                                                3,279.92
                                                
                                             | — | — | — | — | — | — | — | — | 
                                                3,837.11
                                                
                                             | 
                                                4,058.03
                                                
                                             | — | 
                                                4,026.14
                                                
                                             | 
                                                3,772.60
                                                
                                             | — | — | — | 
                                                3,621.04
                                                
                                             | 
                                                3,913.38
                                                
                                             | 
                                                3,961.46
                                                
                                             | — | — | 
                                                4,266.26
                                                
                                             | 
| Dividend paid per share | — | — | — | — | — | — | — | 
                                                20.0
                                                
                                             | — | — | 
                                                70.0
                                                
                                             | — | — | — | 
                                                70.0
                                                
                                             | — | — | — | 
                                                50.0
                                                
                                             | — | — | — | — | 
                                                50.0
                                                
                                             | — | — | 
| Interim dividend paid per share | — | — | — | — | — | — | — |  | — | — |  | — | — | — |  | — | — | — |  | — | — | — | — |  | — | — | 
| Basic earnings (loss) per share | — | — | 
                                                -249.91
                                                
                                             | — | — | — | — | 
                                                -236.78
                                                
                                             | — | — | 
                                                170.55
                                                
                                             | 
                                                199.84
                                                
                                             | — | — | 
                                                172.52
                                                
                                             | — | — | 
                                                213.28
                                                
                                             | 
                                                149.17
                                                
                                             | 
                                                174.63
                                                
                                             | — | — | — | 
                                                203.33
                                                
                                             | 
                                                219.41
                                                
                                             | — | 
| Diluted earnings per share | — | — |  | — | — | — | — |  | — | — | 
                                                166.85
                                                
                                             | 
                                                195.50
                                                
                                             | — | — | 
                                                168.77
                                                
                                             | — | — | 
                                                208.65
                                                
                                             | 
                                                145.79
                                                
                                             | 
                                                170.68
                                                
                                             | — | — | — | 
                                                199.30
                                                
                                             | 
                                                215.06
                                                
                                             | — | 
| Equity-to-asset ratio | — | 
                                                0.3138
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.4619
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
                                                0.3419
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.4760
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.4965
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.3663
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.3581
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.4900
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.3679
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.4956
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Rate of return on equity | — | — | 
                                                -0.0724
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                -0.0643
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.0423
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.0527
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.0437
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.0581
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.0366
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.0462
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.0503
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.0589
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Price-earnings ratio | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                11.51
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                9.82
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                7.52
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                6.08
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                8.18
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                6.99
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                6.71
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                6.22
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Payout ratio | — | — | — | — | — | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.4104
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.4058
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.3352
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.2459
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
| Net cash provided by (used in) operating activities | — | — | 
                                                896,171,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
                                                386,892,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                459,770,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                412,153,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                551,208,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) investing activities | — | — | 
                                                640,144,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
                                                -680,173,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                -403,001,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -366,255,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                2,438,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) financing activities | — | — | 
                                                -277,147,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
                                                269,956,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                -117,562,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -43,179,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -425,726,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | — | 
                                                1,896,368,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | 
                                                637,200,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                660,525,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                721,318,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                718,599,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Number of employees | 
                                                47
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                213
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                128
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                81
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                70
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                143
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                214
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                129
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                134
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                219
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                215
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                127
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                212
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                126
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                56
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                19
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                14
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                12
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                44
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                49
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                18
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                18
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                53
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                60
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                26
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                63
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                27
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total shareholder return | — | — | — | 
                                                1.924
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                2.538
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.690
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1.521
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.629
                                                
                                                    
                                                        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
                                                    
                                                
                                             |