Key Financial Data Of Reporting Company
| Concept | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | 2024-04-01 to 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | 2024-04-01 to 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | 2023-04-01 to 2024-03-31 | 2023-04-01 to 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | 2022-04-01 to 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | 2022-04-01 to 2023-03-31 | 2021-04-01 to 2022-03-31 | 2021-04-01 to 2022-03-31 | As at 2022-03-31 | As at 2022-03-31 | As at 2021-03-31 | 2020-04-01 to 2021-03-31 | 2020-04-01 to 2021-03-31 | As at 2021-03-31 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Key financial data of reporting company | |||||||||||||||||||||||||||
| Business results of reporting company | |||||||||||||||||||||||||||
| Net sales | — | — | — | — | — | 
                                                20,529,656,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                20,533,254,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                19,723,498,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                18,841,240,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                18,849,203,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Operating revenue | — | — | — | — | — | — | — | — | 
                                                144,778,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                154,778,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                154,778,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                404,778,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                404,760,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Ordinary profit (loss) | — | — | — | — | — | 
                                                313,207,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -96,150,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -61,164,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                666,939,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -27,298,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                386,127,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                211,259,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                603,786,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                226,075,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                756,937,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) | — | — | — | — | — | — | — | — | 
                                                -19,954,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                11,950,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                145,955,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                398,637,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                285,137,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Share capital | — | — | — | — | — | — | — | 
                                                2,323,272,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                2,323,272,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,323,272,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                2,323,272,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                2,323,272,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total number of issued shares | — | — | — | — | — | — | — | 
                                                15,145,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                15,145,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
                                                15,145,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | — | — | 
                                                15,145,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | 
                                                15,145,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
| Net assets | — | — | — | — | 
                                                6,640,874,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                3,333,364,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                6,653,492,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,487,964,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,610,688,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,315,806,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                6,226,188,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,599,379,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,304,303,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                3,605,954,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | — | — | — | — | 
                                                9,325,971,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                3,376,895,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                9,727,185,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,514,559,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,641,783,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                8,903,483,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                8,645,652,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,658,663,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                9,065,779,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                3,654,405,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets per share | — | — | — | — | 
                                                491.76
                                                
                                             | — | — | 
                                                247.57
                                                
                                             | — | — | — | — | — | 
                                                491.56
                                                
                                             | 
                                                259.05
                                                
                                             | — | 
                                                268.16
                                                
                                             | 
                                                465.93
                                                
                                             | — | — | — | 
                                                459.57
                                                
                                             | 
                                                267.32
                                                
                                             | 
                                                448.32
                                                
                                             | — | — | 
                                                258.33
                                                
                                             | 
| Dividend paid per share | — | — | — | — | — | — | — | — | 
                                                10.00
                                                
                                             | — | — | 
                                                10.00
                                                
                                             | — | — | — | 
                                                10.00
                                                
                                             | — | — | — | 
                                                10.00
                                                
                                             | — | — | — | — | 
                                                10.00
                                                
                                             | — | — | 
| Interim dividend paid per share | — | — | — | — | — | — | — | — |  | — | — |  | — | — | — |  | — | — | — |  | — | — | — | — |  | — | — | 
| Basic earnings (loss) per share | — | — | — | — | — | 
                                                10.67
                                                
                                             | — | — | 
                                                -1.48
                                                
                                             | — | — | 
                                                0.89
                                                
                                             | 
                                                34.90
                                                
                                             | — | — | 
                                                10.84
                                                
                                             | — | — | 
                                                15.18
                                                
                                             | 
                                                29.14
                                                
                                             | 
                                                25.42
                                                
                                             | — | — | — | 
                                                20.34
                                                
                                             | 
                                                29.41
                                                
                                             | — | 
| Diluted earnings per share | — | — | — | — | — |  | — | — |  | — | — |  |  | — | — |  | — | — |  |  |  | — | — | — |  |  | — | 
| Equity-to-asset ratio | — | — | — | — | 
                                                0.710
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.987
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                0.680
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.992
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.992
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.705
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.716
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.984
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.690
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.987
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Rate of return on equity | — | — | — | — | — | 
                                                0.022
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                -0.006
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.003
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.073
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.041
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.033
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.111
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.056
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.080
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.067
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Price-earnings ratio | — | — | — | — | — | 
                                                31.87
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                -229.73
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                425.84
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                10.86
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                34.41
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                24.57
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                16.64
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                19.08
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                28.91
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                19.99
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Payout ratio | — | — | — | — | — | — | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                11.2360
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.9225
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.3432
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.4916
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
| Net cash provided by (used in) operating activities | — | — | — | — | — | 
                                                -17,385,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                713,930,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                662,729,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                196,139,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                227,707,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) investing activities | — | — | — | — | — | 
                                                -49,106,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                -41,030,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                -21,401,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                55,904,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -960,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) financing activities | — | — | — | — | — | 
                                                -185,709,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                -140,839,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                -184,589,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -428,938,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -199,259,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | — | — | — | — | 
                                                5,315,621,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
                                                5,570,415,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                5,018,617,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                4,547,931,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,708,552,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Number of employees | 
                                                17
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                559
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                112
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,492
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,492
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                16
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                788
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                16
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                1,513
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                14
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                14
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,564
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1,629
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                13
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,583
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                13
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                777
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                16
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                984
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                984
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                190
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                940
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                910
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                861
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                852
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total shareholder return | — | — | — | — | — | — | — | 
                                                0.915
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                0.984
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.946
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1.185
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.404
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total return on share price index | — | — | — | — | — | — | — | 
                                                2.134
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                2.168
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.534
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1.450
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.421
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             |