Key Financial Data Of Group
| Concept | As at 2023-12-31 | 2023-10-01 to 2023-12-31 | As at 2023-09-30 | 2022-10-01 to 2023-09-30 | As at 2022-12-31 | 2022-10-01 to 2022-12-31 | 
|---|---|---|---|---|---|---|
| Key financial data of group | ||||||
| Business results of group | ||||||
| Revenue | — | 
                                                8,190,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                36,405,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                7,583,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Profit (loss) before tax | — | 
                                                -131,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,526,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                737,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Profit (loss), attributable to owners of parent | — | 
                                                -397,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                944,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                564,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Comprehensive income, attributable to owners of parent | — | 
                                                -572,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,758,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                176,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Equity attributable to owners of parent | 
                                                31,335,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                32,462,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                29,900,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Total assets | 
                                                48,291,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                51,153,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                46,298,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Basic earnings (loss) per share | — | 
                                                -3.11
                                                
                                             | — | 
                                                7.35
                                                
                                             | — | 
                                                4.35
                                                
                                             | 
| Diluted earnings (loss) per share | — |  | — | 
                                                7.34
                                                
                                             | — | 
                                                4.34
                                                
                                             | 
| Ratio of owners' equity to gross assets | 
                                                0.649
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.635
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.646
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Cash flows from (used in) operating activities | — | 
                                                -649,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                6,233,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -293,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Cash flows from (used in) investing activities | — | 
                                                -668,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -1,743,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                540,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Cash flows from (used in) financing activities | — | 
                                                -1,328,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -5,079,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -2,056,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Cash and cash equivalents | 
                                                13,850,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                16,510,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                14,566,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — |