Key Financial Data Of Reporting Company
| Concept | As at 2025-03-31 | 2024-04-01 to 2025-03-31 | As at 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 reporting company | |||||||||||||||||||||
| Business results of reporting company | |||||||||||||||||||||
| Net sales | — | 
                                                3,077,721,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                3,077,721,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,016,061,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,016,061,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                2,322,112,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                2,322,112,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,667,991,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,667,991,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,009,932,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,009,932,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Ordinary profit (loss) | — | 
                                                271,729,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                267,848,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                327,920,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                330,477,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                25,291,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                28,814,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -126,038,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -122,631,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -361,279,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -361,029,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) | — | — | — | — | 
                                                153,518,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                328,650,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                19,046,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -160,604,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -364,872,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Equity in earnings (losses) of affiliates if equity method is applied | — | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Share capital | — | — | 
                                                1,838,882,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1,838,882,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,838,882,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1,838,882,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,838,882,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total number of issued shares | — | — | 
                                                3,152,400
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | — | — | 
                                                3,152,400
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
                                                3,152,400
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | — | — | 
                                                3,152,400
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | 
                                                3,152,400
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
| Net assets | 
                                                3,611,482,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,594,858,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                3,457,844,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,445,066,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,113,626,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,124,151,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                3,095,483,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,092,208,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,250,208,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                3,250,060,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | 
                                                4,092,428,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,078,930,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                3,919,796,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,911,733,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,834,751,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,842,109,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                3,472,189,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,472,984,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,477,303,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                3,481,010,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets per share | 
                                                1,148.27
                                                
                                             | — | 
                                                1,142.98
                                                
                                             | — | — | — | — | 
                                                1,099.42
                                                
                                             | 
                                                1,095.36
                                                
                                             | — | 
                                                989.95
                                                
                                             | 
                                                993.30
                                                
                                             | — | — | — | 
                                                983.23
                                                
                                             | 
                                                982.19
                                                
                                             | 
                                                1,032.07
                                                
                                             | — | — | 
                                                1,032.02
                                                
                                             | 
| Dividend paid per share | — | — | — | — |  |  | — | — | — |  | — | — | — |  | — | — | — | — |  | — | — | 
| Interim dividend paid per share | — | — | — | — |  |  | — | — | — |  | — | — | — |  | — | — | — | — |  | — | — | 
| Basic earnings (loss) per share | — | 
                                                49.96
                                                
                                             | — | — | 
                                                48.81
                                                
                                             | 
                                                104.49
                                                
                                             | 
                                                105.33
                                                
                                             | — | — | 
                                                6.05
                                                
                                             | — | — | 
                                                7.17
                                                
                                             | 
                                                -51.01
                                                
                                             | 
                                                -49.93
                                                
                                             | — | — | — | 
                                                -116.11
                                                
                                             | 
                                                -116.03
                                                
                                             | — | 
| Diluted earnings per share | — |  | — | — |  |  |  | — | — |  | — | — |  |  |  | — | — | — |  |  | — | 
| Equity-to-asset ratio | 
                                                0.882
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.881
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.882
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.881
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.812
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.813
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.892
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.890
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.935
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.934
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Rate of return on equity | — | 
                                                0.044
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.044
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.100
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.101
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.006
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.007
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Price-earnings ratio | — | 
                                                35.13
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                35.96
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                36.80
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                36.51
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                454.40
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                383.40
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Payout ratio | — | — | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
| Net cash provided by (used in) operating activities | — | 
                                                93,247,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                660,976,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                -37,573,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -39,923,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                36,360,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) investing activities | — | 
                                                -167,107,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -500,029,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                465,910,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -77,348,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                68,624,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) financing activities | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -291,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                -108,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -90,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -1,508,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | 
                                                2,529,833,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                2,603,750,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                2,435,996,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                2,002,540,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,112,353,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Number of employees | 
                                                56
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                44
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                56
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                63
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                43
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                44
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                64
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                67
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                42
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                63
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                42
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                2
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total shareholder return | — | — | 
                                                0.881
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1.930
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.381
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                0.711
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.387
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total return on share price index | — | — | 
                                                1.895
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1.973
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.428
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1.387
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.393
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             |