Employees
| Concept | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2022-03-31 | As at 2022-03-31 | As at 2021-03-31 | As at 2021-03-31 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Employees | |||||||||||||||||
| Information about reporting company | |||||||||||||||||
| Information about employees of reporting company | |||||||||||||||||
| Number of employees | 
                                                122
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                445
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                69
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                13
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                69
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                715
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                907
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                527
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                532
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                904
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                911
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                535
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                539
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                913
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                926
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                543
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average age (Years) | — | — | — | — | — | — | — | 
                                                44.1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
| Average length of service (Years) | — | — | — | — | — | — | — | 
                                                18.9
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
| Average annual salary | — | — | — | — | — | — | — | 
                                                6,590,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — |