Key Financial Data Of Reporting Company
| Concept | 2023-01-01 to 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 | 2019-11-01 to 2020-12-31 | As at 2020-12-31 | As at 2019-10-31 | 2018-11-01 to 2019-10-31 | 
|---|---|---|---|---|---|---|---|---|---|---|
| Key financial data of reporting company | ||||||||||
| Business results of reporting company | ||||||||||
| Net sales | 
                                                1,000,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Ordinary profit (loss) | 
                                                344,184,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -359,233,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -220,892,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -269,562,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -255,606,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Profit (loss) | 
                                                260,330,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -392,427,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -228,718,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -271,219,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -256,186,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Equity in earnings (losses) of affiliates if equity method is applied | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Share capital | — | 
                                                854,087,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                100,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                100,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                100,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                100,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Total number of issued shares | — | 
                                                11,604,600
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
                                                5,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                5,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | 
                                                5,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                5,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
| Net assets | — | 
                                                3,104,768,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,336,263,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                178,891,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                8,009,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                279,228,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Total assets | — | 
                                                3,313,902,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,374,566,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                205,767,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                56,983,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                294,068,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net assets per share | — | 
                                                267.55
                                                
                                             | — | 
                                                -122.77
                                                
                                             | 
                                                -107.03
                                                
                                             | — | — | 
                                                -84,539.31
                                                
                                             | 
                                                -45,788.18
                                                
                                             | — | 
| Dividend paid per share |  | — |  | — | — |  |  | — | — |  | 
| Interim dividend paid per share |  | — |  | — | — |  |  | — | — |  | 
| Basic earnings (loss) per share | 
                                                25.42
                                                
                                             | — | 
                                                -42.06
                                                
                                             | — | — | 
                                                -30.09
                                                
                                             | 
                                                -38,751.13
                                                
                                             | — | — | 
                                                -37,032.98
                                                
                                             | 
| Diluted earnings per share | 
                                                23.07
                                                
                                             | — |  | — | — |  |  | — | — |  | 
| Equity-to-asset ratio | — | 
                                                0.937
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.972
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.869
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.141
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.950
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Rate of return on equity | 
                                                0.117
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Price-earnings ratio | 
                                                28.3
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        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 | 
                                                454,425,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -363,482,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -196,320,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net cash provided by (used in) investing activities | 
                                                -11,099,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -32,737,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -250,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net cash provided by (used in) financing activities | 
                                                1,486,235,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,544,285,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                368,201,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Cash and cash equivalents | — | 
                                                3,266,408,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,336,847,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                188,782,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Number of employees | — | 
                                                15
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                13
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                11
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                10
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                9
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Average number of temporary employees | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
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                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
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                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Total shareholder return | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
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                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Total return on share price index | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
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                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
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                                                        xbrli:pure
                                                    
                                                
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