Key Financial Data Of Reporting Company
| Concept | 2024-04-01 to 2025-03-31 | As at 2025-03-31 | As at 2024-03-31 | 2023-04-01 to 2024-03-31 | As at 2023-03-31 | 2022-04-01 to 2023-03-31 | 2021-04-01 to 2022-03-31 | As at 2022-03-31 | 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 | 
                                                5,444,575,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                5,839,861,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                6,004,926,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,519,442,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                6,785,071,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Ordinary profit (loss) | 
                                                4,245,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -28,092,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -602,408,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -1,106,523,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -1,282,417,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) | 
                                                -62,325,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -158,820,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -804,909,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                390,009,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -1,013,873,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Equity in earnings (losses) of affiliates if equity method is applied | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Share capital | — | 
                                                62,344,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                50,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                50,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                50,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,480,180,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total number of issued shares | — | 
                                                5,186,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                5,100,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
                                                5,100,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | 
                                                5,100,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
                                                5,100,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
| Net assets | — | 
                                                416,658,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                451,918,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                610,738,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,415,648,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,025,638,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | — | 
                                                1,986,701,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,005,845,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,366,866,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                3,243,952,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,899,981,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets per share | — | 
                                                81.50
                                                
                                             | 
                                                90.44
                                                
                                             | — | 
                                                122.22
                                                
                                             | — | — | 
                                                283.30
                                                
                                             | — | 
                                                205.25
                                                
                                             | 
| Dividend paid per share |  | — | — |  | — |  |  | — |  | — | 
| Interim dividend paid per share |  | — | — |  | — |  |  | — |  | — | 
| Basic earnings (loss) per share | 
                                                -12.46
                                                
                                             | — | — | 
                                                -31.78
                                                
                                             | — | 
                                                -161.08
                                                
                                             | 
                                                78.05
                                                
                                             | — | 
                                                -202.89
                                                
                                             | — | 
| Diluted earnings per share |  | — | — |  | — |  |  | — |  | — | 
| Equity-to-asset ratio | — | 
                                                0.209
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.225
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.258
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.436
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.209
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Rate of return on equity | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.320
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Price-earnings ratio | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Payout ratio | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) operating activities | 
                                                -67,111,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -25,414,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -582,507,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -1,516,264,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -839,250,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) investing activities | 
                                                -167,199,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -14,346,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -119,118,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,587,435,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                293,690,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) financing activities | 
                                                134,380,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -69,391,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                108,415,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -1,481,624,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                366,664,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | — | 
                                                166,232,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                266,177,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                375,329,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                968,540,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                378,993,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Number of employees | — | 
                                                527
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                597
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                719
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                875
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1,020
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | — | 
                                                101
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                119
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                151
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                180
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                183
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total shareholder return | — | 
                                                0.532
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.716
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.934
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.970
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.000
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total return on share price index | — | 
                                                1.895
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1.973
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.428
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                1.387
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.393
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             |