Key Financial Data Of Reporting Company
| Concept | 2023-01-01 to 2023-12-31 | As at 2023-12-31 | As at 2023-12-31 | As at 2023-12-31 | As at 2023-12-31 | As at 2023-12-31 | 2022-01-01 to 2022-12-31 | As at 2022-12-31 | As at 2021-12-31 | 2021-01-01 to 2021-12-31 | 2020-01-01 to 2020-12-31 | As at 2020-12-31 | As at 2019-12-31 | 2019-01-01 to 2019-12-31 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Key financial data of reporting company | ||||||||||||||
| Business results of reporting company | ||||||||||||||
| Net sales | 
                                                1,523,120,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1,480,636,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,215,796,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                882,868,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                671,664,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Ordinary profit (loss) | 
                                                143,037,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                455,536,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                298,606,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                126,717,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                62,555,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Profit (loss) | 
                                                59,491,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                297,162,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                201,998,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                86,353,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                80,347,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Equity in earnings (losses) of affiliates if equity method is applied | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Share capital | — | 
                                                370,618,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                369,890,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                85,494,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                85,494,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                85,494,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Total number of issued shares | — | 
                                                8,207,100
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | — | — | 
                                                8,136,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                1,075,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | 
                                                1,075,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                1,075,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
| Net assets | — | 
                                                1,378,084,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1,316,974,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                451,056,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                249,057,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                162,704,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Total assets | — | 
                                                3,224,518,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                2,908,069,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,963,776,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,308,554,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                826,489,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net assets per share | — | 
                                                167.89
                                                
                                             | — | — | — | — | — | 
                                                161.87
                                                
                                             | 
                                                60.70
                                                
                                             | — | — | 
                                                33.52
                                                
                                             | 
                                                11.94
                                                
                                             | — | 
| Dividend paid per share |  | — | — | — | — | — |  | — | — |  |  | — | — |  | 
| Interim dividend paid per share |  | — | — | — | — | — |  | — | — |  |  | — | — |  | 
| Basic earnings (loss) per share | 
                                                7.29
                                                
                                             | — | — | — | — | — | 
                                                39.13
                                                
                                             | — | — | 
                                                27.18
                                                
                                             | 
                                                11.62
                                                
                                             | — | — | 
                                                74.74
                                                
                                             | 
| Diluted earnings per share | 
                                                6.97
                                                
                                             | — | — | — | — | — | 
                                                38.61
                                                
                                             | — | — |  |  | — | — |  | 
| Equity-to-asset ratio | — | 
                                                0.427
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                0.453
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.230
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.190
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.197
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Rate of return on equity | 
                                                0.044
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                0.336
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.577
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.419
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.656
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Price-earnings ratio | 
                                                76.1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                20.6
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Payout ratio | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Net cash provided by (used in) operating activities | 
                                                -148,820,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                209,584,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                400,275,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                285,706,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net cash provided by (used in) investing activities | 
                                                -604,417,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                -47,922,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                13,309,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -45,498,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net cash provided by (used in) financing activities | 
                                                333,951,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                826,690,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -40,084,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                197,691,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Cash and cash equivalents | — | 
                                                1,738,947,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                2,158,234,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,169,882,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                796,380,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Number of employees | — | 
                                                141
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                32
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                43
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                17
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                49
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                98
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                94
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                81
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                64
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Average number of temporary employees | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Total shareholder return | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Total return on share price index | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — |