Key Financial Data Of Reporting Company
| Concept | 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 | 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 | — | — | — | 
                                                32,570,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                23,501,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                22,409,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                30,748,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                21,951,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                31,559,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                24,011,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                32,506,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                24,384,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                31,541,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Ordinary profit (loss) | — | — | — | 
                                                443,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                339,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -1,001,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -219,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -983,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                58,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -2,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,022,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                690,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                582,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) | — | — | — | — | — | — | — | 
                                                143,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -777,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -349,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                249,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                643,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Share capital | — | — | — | — | — | 
                                                4,304,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                4,304,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,304,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                4,304,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                4,304,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total number of issued shares | — | — | — | — | — | 
                                                4,261,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                4,261,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
                                                4,261,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | — | — | 
                                                4,261,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | 
                                                4,261,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
| Net assets | — | — | 
                                                19,167,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                9,426,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                18,460,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                9,385,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                10,253,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                18,534,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                18,501,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                10,994,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                18,014,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                11,055,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | — | — | 
                                                49,851,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                33,051,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                49,548,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                34,868,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                35,912,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                48,571,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                49,453,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                35,103,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                47,124,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                34,589,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets per share | — | — | 
                                                5,312.46
                                                
                                             | — | — | 
                                                2,581.63
                                                
                                             | — | — | — | — | — | — | 
                                                5,116.02
                                                
                                             | 
                                                2,570.03
                                                
                                             | — | 
                                                2,802.53
                                                
                                             | 
                                                5,130.65
                                                
                                             | — | — | — | 
                                                5,119.99
                                                
                                             | 
                                                3,004.58
                                                
                                             | 
                                                5,006.49
                                                
                                             | — | — | 
                                                3,034.03
                                                
                                             | 
| Dividend paid per share | — | — | — | — | — | — | — | 
                                                50.00
                                                
                                             | — | — | 
                                                50.00
                                                
                                             | — | — | — | 
                                                50.00
                                                
                                             | — | — | — | 
                                                50.00
                                                
                                             | — | — | — | — | 
                                                50.00
                                                
                                             | — | — | 
| Interim dividend paid per share | — | — | — | — | — | — | — | 
                                                0.00
                                                
                                             | — | — | 
                                                0.00
                                                
                                             | — | — | — | 
                                                0.00
                                                
                                             | — | — | — | 
                                                0.00
                                                
                                             | — | — | — | — | 
                                                0.00
                                                
                                             | — | — | 
| Basic earnings (loss) per share | — | — | — | 
                                                81.72
                                                
                                             | — | — | — | 
                                                39.33
                                                
                                             | — | — | 
                                                -212.84
                                                
                                             | 
                                                -50.14
                                                
                                             | — | — | 
                                                -95.59
                                                
                                             | — | — | 
                                                94.07
                                                
                                             | 
                                                68.32
                                                
                                             | 
                                                194.33
                                                
                                             | — | — | — | 
                                                176.96
                                                
                                             | 
                                                137.75
                                                
                                             | — | 
| Diluted earnings per share | — | — | — |  | — | — | — |  | — | — |  |  | — | — |  | — | — |  |  |  | — | — | — |  |  | — | 
| Equity-to-asset ratio | — | — | 
                                                0.384
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.285
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                0.373
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.269
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.285
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.381
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.374
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.313
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.382
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.319
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Rate of return on equity | — | — | — | 
                                                0.016
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.015
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                -0.079
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                -0.010
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                -0.033
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.018
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.023
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.038
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.060
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.028
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Price-earnings ratio | — | — | — | 
                                                18.1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                37.6
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                19.5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                30.5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                10.7
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                14.9
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                19.1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Payout ratio | — | — | — | — | — | — | — | 
                                                1.271
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.732
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.283
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
| Net cash provided by (used in) operating activities | — | — | — | 
                                                -265,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                296,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                -916,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,801,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                1,503,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) investing activities | — | — | — | 
                                                -1,655,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                -3,139,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                -394,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                35,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -1,024,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) financing activities | — | — | — | 
                                                -305,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                1,447,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                144,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -793,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                29,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | — | — | 
                                                7,021,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                9,200,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                10,529,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                11,645,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                10,505,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Number of employees | 
                                                1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                34
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                855
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                75
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                330
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                34
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                746
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                295
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                887
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                352
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                349
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                872
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                809
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                347
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                760
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                352
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                158
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                36
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                84
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                117
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                78
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                155
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                87
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                98
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                171
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                161
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                90
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                168
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                92
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total shareholder return | — | — | — | — | — | 
                                                0.699
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                0.747
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.804
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                0.882
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.083
                                                
                                                    
                                                        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
                                                    
                                                
                                             |