Key Financial Data Of Reporting Company
| Concept | As at 2024-12-31 | 2024-01-01 to 2024-12-31 | 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 | 2020-01-01 to 2020-12-31 | As at 2020-12-31 | 
|---|---|---|---|---|---|---|---|---|---|---|
| Key financial data of reporting company | ||||||||||
| Business results of reporting company | ||||||||||
| Ordinary profit (loss) | — | 
                                                -962,035,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -1,127,594,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -384,202,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -792,615,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -604,610,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) | — | 
                                                -964,455,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -1,130,014,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -386,622,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -795,035,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -636,649,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Equity in earnings (losses) of affiliates if equity method is applied | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Share capital | 
                                                4,047,254,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                4,045,977,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,787,552,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,537,519,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,346,520,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total number of issued shares | 
                                                43,301,765
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | 
                                                43,276,765
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
                                                39,579,865
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                38,958,665
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | 
                                                7,179,868
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
| Net assets | 
                                                4,725,497,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                5,687,452,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,300,617,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,185,334,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                2,598,379,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | 
                                                4,800,172,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                5,778,946,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,641,032,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,271,049,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                2,674,261,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets per share | 
                                                108.97
                                                
                                             | — | — | 
                                                131.26
                                                
                                             | — | 
                                                108.48
                                                
                                             | 
                                                107.30
                                                
                                             | — | — | 
                                                361.19
                                                
                                             | 
| Dividend paid per share | — |  |  | — |  | — | — |  |  | — | 
| Interim dividend paid per share | — |  |  | — |  | — | — |  |  | — | 
| Basic earnings (loss) per share | — | 
                                                -22.28
                                                
                                             | 
                                                -27.25
                                                
                                             | — | 
                                                -9.87
                                                
                                             | — | — | 
                                                -20.75
                                                
                                             | 
                                                -89.64
                                                
                                             | — | 
| Diluted earnings per share | — |  |  | — |  | — | — |  |  | — | 
| Equity-to-asset ratio | 
                                                0.983
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.983
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.925
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.979
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.970
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Rate of return on equity | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Price-earnings ratio | — | 
                                                
                                                
                                                    
                                                        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 | — | 
                                                -887,809,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -873,076,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -107,176,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -777,140,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -300,645,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) investing activities | — | 
                                                557,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -5,316,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -4,032,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) financing activities | — | 
                                                2,500,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,913,086,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                487,615,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                2,373,653,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                996,346,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | 
                                                4,670,939,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                5,555,691,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,520,997,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,140,558,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                2,548,077,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Number of employees | 
                                                25
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                28
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                19
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                14
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                12
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                4
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                6
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total shareholder return | 
                                                0.802
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total return on share price index | 
                                                0.912
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             |