Key Financial Data Of Group
| Concept | 2024-10-01 to 2025-03-31 | As at 2025-03-31 | As at 2024-09-30 | 2023-10-01 to 2024-09-30 | 2023-10-01 to 2024-03-31 | As at 2024-03-31 | 
|---|---|---|---|---|---|---|
| Key financial data of group | ||||||
| Business results of group | ||||||
| Revenue | 
                                                14,291,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                26,312,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                13,280,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) before tax | 
                                                1,801,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                2,549,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,631,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss), attributable to owners of parent | 
                                                3,723,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -8,463,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                119,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Comprehensive income, attributable to owners of parent | 
                                                561,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -7,710,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                676,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Equity attributable to owners of parent | — | 
                                                24,531,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                24,105,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                32,514,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | — | 
                                                37,436,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                41,191,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                50,619,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Basic earnings (loss) per share | 
                                                29.08
                                                
                                             | — | — | 
                                                -66.12
                                                
                                             | 
                                                0.93
                                                
                                             | — | 
| Diluted earnings (loss) per share |  | — | — |  | 
                                                0.93
                                                
                                             | — | 
| Ratio of owners' equity to gross assets | — | 
                                                0.655
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.585
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.642
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Cash flows from (used in) operating activities | 
                                                1,369,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,671,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -12,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash flows from (used in) investing activities | 
                                                -9,370,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -718,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                74,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash flows from (used in) financing activities | 
                                                2,724,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -2,977,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -1,593,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | — | 
                                                8,532,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                14,633,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                15,148,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             |