Key Financial Data Of Reporting Company
| Concept | As at 2023-12-31 | 2023-10-01 to 2023-12-31 | 2022-10-01 to 2023-09-30 | As at 2023-09-30 | As at 2022-12-31 | 2022-10-01 to 2022-12-31 | 
|---|---|---|---|---|---|---|
| Key financial data of reporting company | ||||||
| Business results of reporting company | ||||||
| Net sales | — | 
                                                18,690,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                69,250,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                17,365,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Ordinary profit (loss) | — | 
                                                -169,113,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -852,660,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -157,476,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Profit (loss) | — | 
                                                -169,486,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -854,151,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -157,849,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Equity in earnings (losses) of affiliates if equity method is applied | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Share capital | 
                                                354,595,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                97,546,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                59,877,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Total number of issued shares | 
                                                6,298,500
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | 
                                                5,522,200
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                5,380,700
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
| Net assets | 
                                                2,361,483,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                2,021,702,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,632,614,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Total assets | 
                                                2,844,699,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                2,618,657,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,048,096,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Dividend paid per share | — |  |  | — | — |  | 
| Basic earnings (loss) per share | — | 
                                                -29.53
                                                
                                             | 
                                                -158.46
                                                
                                             | — | — | 
                                                -29.34
                                                
                                             | 
| Diluted earnings per share | — |  |  | — | — |  | 
| Equity-to-asset ratio | 
                                                0.827
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.766
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.862
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — |