Key Financial Data Of Group
| Concept | 2023-10-01 to 2024-09-30 | As at 2024-09-30 | 2022-10-01 to 2023-09-30 | As at 2023-09-30 | 2021-10-01 to 2022-09-30 | As at 2022-09-30 | 2020-10-01 to 2021-09-30 | As at 2021-09-30 | 2019-10-01 to 2020-09-30 | As at 2020-09-30 | 
|---|---|---|---|---|---|---|---|---|---|---|
| Key financial data of group | ||||||||||
| Business results of group | ||||||||||
| Net sales | 
                                                80,038,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                69,250,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                391,829,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                289,756,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                467,616,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Ordinary profit (loss) | 
                                                -754,961,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -852,660,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -330,339,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -299,676,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -116,341,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net assets | — | 
                                                2,108,192,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,021,702,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,789,187,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,506,149,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,188,521,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | — | 
                                                2,757,113,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,618,657,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,208,691,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,635,625,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,350,242,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets per share | — | 
                                                306.87
                                                
                                             | — | 
                                                363.45
                                                
                                             | — | 
                                                517.75
                                                
                                             | — | 
                                                578.17
                                                
                                             | — | 
                                                599.97
                                                
                                             | 
| Basic earnings (loss) per share | 
                                                -118.21
                                                
                                             | — | 
                                                -158.46
                                                
                                             | — | 
                                                -68.33
                                                
                                             | — | 
                                                -72.51
                                                
                                             | — | 
                                                -106.70
                                                
                                             | — | 
| Diluted earnings per share |  | — |  | — |  | — |  | — |  | — | 
| Equity-to-asset ratio | — | 
                                                0.758
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.766
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.868
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.951
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.931
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Rate of return on equity | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Price-earnings ratio | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) operating activities | 
                                                -661,166,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -689,095,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                15,796,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -560,922,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -146,461,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) investing activities | 
                                                -121,363,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -120,875,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -254,383,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) financing activities | 
                                                838,233,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                69,164,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                603,112,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                595,904,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,082,523,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | — | 
                                                1,816,943,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,761,239,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,502,046,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,137,520,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,102,538,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Number of employees | — | 
                                                15
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                13
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                12
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                11
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                9
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             |