Key Financial Data Of Reporting Company
| Concept | As at 2024-06-30 | 2024-01-01 to 2024-06-30 | 2023-01-01 to 2023-12-31 | As at 2023-12-31 | As at 2023-06-30 | 2023-01-01 to 2023-06-30 | 
|---|---|---|---|---|---|---|
| Key financial data of reporting company | ||||||
| Business results of reporting company | ||||||
| Net sales | — | 
                                                778,357,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,523,120,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                723,296,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Ordinary profit (loss) | — | 
                                                -108,998,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                141,757,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                141,191,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Profit (loss) | — | 
                                                -85,768,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                58,882,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                96,254,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Equity in earnings (losses) of affiliates if equity method is applied | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Share capital | 
                                                370,734,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                370,618,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                369,890,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Total number of issued shares | 
                                                8,218,800
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | 
                                                8,207,100
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                8,136,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
| Net assets | 
                                                1,292,266,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,377,475,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,413,228,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Total assets | 
                                                2,960,732,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                3,223,909,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,889,388,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Dividend paid per share | — |  |  | — | — |  | 
| Basic earnings (loss) per share | — | 
                                                -10.44
                                                
                                             | 
                                                7.22
                                                
                                             | — | — | 
                                                11.83
                                                
                                             | 
| Diluted earnings per share | — |  | 
                                                6.90
                                                
                                             | — | — | 
                                                11.34
                                                
                                             | 
| Equity-to-asset ratio | 
                                                0.436
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.427
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.489
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) operating activities | — | 
                                                55,244,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -148,820,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                11,347,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net cash provided by (used in) investing activities | — | 
                                                -45,719,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -604,417,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -121,449,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net cash provided by (used in) financing activities | — | 
                                                -138,964,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                333,951,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                55,859,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Cash and cash equivalents | 
                                                1,609,507,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,738,947,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,103,991,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — |