Key Financial Data Of Reporting Company
| Concept | As at 2024-03-31 | 2024-01-01 to 2024-03-31 | 2023-01-01 to 2023-12-31 | As at 2023-12-31 | As at 2023-03-31 | 2023-01-01 to 2023-03-31 | 
|---|---|---|---|---|---|---|
| Key financial data of reporting company | ||||||
| Business results of reporting company | ||||||
| Net sales | — | 
                                                10,745,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                61,112,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                7,070,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Ordinary profit (loss) | — | 
                                                -223,692,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -586,187,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -167,047,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Profit (loss) | — | 
                                                -224,277,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -589,211,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -168,089,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Equity in earnings (losses) of affiliates if equity method is applied | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Share capital | 
                                                1,284,810,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,283,445,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,273,915,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Total number of issued shares | 
                                                7,915,800
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | 
                                                7,894,300
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                7,803,300
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
| Net assets | 
                                                2,995,290,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                3,203,469,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,605,531,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Total assets | 
                                                3,903,842,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                4,214,809,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,594,521,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Dividend paid per share | — |  |  | — | — |  | 
| Basic earnings (loss) per share | — | 
                                                -28.38
                                                
                                             | 
                                                -75.42
                                                
                                             | — | — | 
                                                -21.56
                                                
                                             | 
| Diluted earnings per share | — |  |  | — | — |  | 
| Equity-to-asset ratio | 
                                                0.764
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.760
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.785
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — |