Key Financial Data Of Group
| Concept | As at 2025-03-31 | 2024-04-01 to 2025-03-31 | As at 2025-03-31 | 2024-04-01 to 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 group | ||||||||||||||||||||
| Business results of group | ||||||||||||||||||||
| Net sales | — | 
                                                4,589,136,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,533,473,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,530,970,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,573,141,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,881,885,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                4,808,345,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,347,305,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,073,447,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                2,216,136,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,868,982,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Ordinary profit (loss) | — | 
                                                115,374,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                111,013,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                68,589,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                80,743,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -208,785,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -244,304,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -347,694,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -358,491,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                6,231,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                48,545,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) attributable to owners of parent | — | 
                                                176,882,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                111,117,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                -238,625,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -672,369,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                37,109,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Comprehensive income | — | 
                                                176,882,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                111,117,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                -238,625,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -671,733,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                37,002,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net assets | 
                                                1,358,518,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,458,678,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,181,635,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,281,290,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                990,176,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                957,395,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,188,427,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,183,982,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,837,273,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,809,274,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | 
                                                3,280,733,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,354,207,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                3,517,496,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,586,071,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,544,259,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,073,518,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                2,840,459,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,591,948,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,433,341,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                3,204,764,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets per share | 
                                                83.62
                                                
                                             | — | 
                                                89.79
                                                
                                             | — | — | — | 
                                                72.74
                                                
                                             | 
                                                78.87
                                                
                                             | — | 
                                                62.74
                                                
                                             | 
                                                60.64
                                                
                                             | — | — | — | 
                                                75.48
                                                
                                             | 
                                                75.20
                                                
                                             | 
                                                117.40
                                                
                                             | — | — | 
                                                115.61
                                                
                                             | 
| Basic earnings (loss) per share | — | 
                                                10.89
                                                
                                             | — | 
                                                10.92
                                                
                                             | 
                                                11.19
                                                
                                             | 
                                                7.00
                                                
                                             | — | — | 
                                                -12.76
                                                
                                             | — | — | 
                                                -15.14
                                                
                                             | 
                                                -41.25
                                                
                                             | 
                                                -42.86
                                                
                                             | — | — | — | 
                                                -0.51
                                                
                                             | 
                                                2.38
                                                
                                             | — | 
| Diluted earnings per share | — | 
                                                10.18
                                                
                                             | — | 
                                                10.21
                                                
                                             | 
                                                11.12
                                                
                                             | 
                                                6.95
                                                
                                             | — | — |  | — | — |  |  |  | — | — | — |  | 
                                                2.31
                                                
                                             | — | 
| Equity-to-asset ratio | 
                                                0.414
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.435
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.336
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.357
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.389
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.311
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.418
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.457
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.535
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.565
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Rate of return on equity | — | 
                                                0.139
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.129
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.156
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.104
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.021
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Price-earnings ratio | — | 
                                                19.2
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                19.2
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                26.6
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                42.5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                303.4
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) operating activities | — | 
                                                -37,504,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                316,495,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                -324,589,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -313,237,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                241,016,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) investing activities | — | 
                                                -50,930,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -94,974,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                -298,645,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -145,284,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -279,635,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) financing activities | — | 
                                                -68,740,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                353,910,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                317,740,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                14,883,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                85,665,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | 
                                                1,767,036,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1,924,211,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,348,779,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,654,274,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,099,531,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Number of employees | 
                                                141
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                141
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                152
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                152
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                117
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                192
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                197
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                159
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                175
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                153
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                7
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                7
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                9
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                9
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                19
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                24
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                28
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                27
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                37
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                25
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             |