Key Financial Data Of Reporting Company
| Concept | 2023-07-01 to 2023-12-31 | As at 2023-12-31 | 2023-10-01 to 2023-12-31 | As at 2023-06-30 | 2022-07-01 to 2023-06-30 | 2022-07-01 to 2022-12-31 | 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 | 
                                                815,822,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,335,656,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                599,487,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Ordinary profit (loss) | 
                                                -96,491,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -334,258,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -199,338,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Profit (loss) | 
                                                -103,971,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -295,508,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -212,219,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Equity in earnings (losses) of affiliates if equity method is applied | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Share capital | — | 
                                                50,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                50,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                50,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Total number of issued shares | — | 
                                                4,351,308
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
                                                4,351,308
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | 
                                                4,351,308
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
| Net assets | — | 
                                                751,986,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                854,787,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                936,095,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Total assets | — | 
                                                1,541,867,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,681,545,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,578,830,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Dividend paid per share |  | — | — | — |  |  | — | — | 
| Basic earnings (loss) per share | 
                                                -27.28
                                                
                                             | — | 
                                                -13.24
                                                
                                             | — | 
                                                -77.53
                                                
                                             | 
                                                -55.68
                                                
                                             | — | 
                                                -20.81
                                                
                                             | 
| Diluted earnings per share |  | — | — | — |  |  | — | — | 
| Equity-to-asset ratio | — | 
                                                0.488
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.508
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.593
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) operating activities | 
                                                -91,907,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -223,137,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -183,778,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Net cash provided by (used in) investing activities | 
                                                -142,005,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                172,814,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -2,626,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Net cash provided by (used in) financing activities | 
                                                -20,483,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                94,375,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -59,899,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Cash and cash equivalents | — | 
                                                453,964,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                708,361,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                418,005,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — |