Key Financial Data Of Group
| Concept | 2023-04-01 to 2023-12-31 | As at 2023-12-31 | 2023-10-01 to 2023-12-31 | As at 2023-03-31 | 2022-04-01 to 2023-03-31 | As at 2022-12-31 | 2022-04-01 to 2022-12-31 | 2022-10-01 to 2022-12-31 | 
|---|---|---|---|---|---|---|---|---|
| Key financial data of group | ||||||||
| Business results of group | ||||||||
| Revenue | 
                                                112,728,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                39,413,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                144,175,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                109,919,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                38,783,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Profit (loss) before tax | 
                                                30,973,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                30,489,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                28,422,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss), attributable to owners of parent | 
                                                24,002,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                7,826,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                22,812,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                22,674,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                7,452,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Comprehensive income, attributable to owners of parent | 
                                                27,397,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                22,854,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                22,888,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Equity attributable to owners of parent | — | 
                                                215,007,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                195,625,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                195,660,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Total assets | — | 
                                                247,830,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                237,451,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                231,876,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Basic earnings (loss) per share | 
                                                356.37
                                                
                                             | — | 
                                                116.20
                                                
                                             | — | 
                                                338.70
                                                
                                             | — | 
                                                336.65
                                                
                                             | 
                                                110.64
                                                
                                             | 
| Diluted earnings (loss) per share |  | — | — | — |  | — |  | — | 
| Ratio of owners' equity to gross assets | — | 
                                                0.868
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.824
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.844
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
| Cash flows from (used in) operating activities | 
                                                8,126,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                26,170,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                12,618,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash flows from (used in) investing activities | 
                                                -2,654,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -17,631,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -9,421,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash flows from (used in) financing activities | 
                                                -9,046,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -9,605,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -8,922,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | — | 
                                                57,323,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                60,047,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                54,919,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — |