Notes - Segment Information
| Concept | As at 2024-09-30 | 2024-04-01 to 2024-09-30 | 2024-04-01 to 2024-09-30 | 2024-04-01 to 2024-09-30 | 2024-04-01 to 2024-09-30 | 2024-04-01 to 2024-09-30 | As at 2024-03-31 | 2023-04-01 to 2023-09-30 | 2023-04-01 to 2023-09-30 | 2023-04-01 to 2023-09-30 | 2023-04-01 to 2023-09-30 | 2023-04-01 to 2023-09-30 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Notes - Segment information | ||||||||||||
| Segment information | ||||||||||||
| Revenue | ||||||||||||
| Revenue from external customers | — | 
                                                10,836,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                79,332,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                68,496,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                79,332,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                60,988,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                12,325,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                73,314,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                73,314,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Intersegment revenue | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Revenue | — | 
                                                10,836,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                79,332,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                68,496,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                79,332,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                60,988,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                12,325,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                73,314,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                73,314,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Profit (loss) before tax | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                18,198,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                21,146,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Assets | 
                                                268,542,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                263,404,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — |