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 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 | 
                                                304
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                633
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                569
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                295
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,895
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                663
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                569
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                566
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,988
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,998
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                567
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                569
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                2,059
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                2,130
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                579
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average age (Years) | — | — | — | — | — | — | 
                                                44.0
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Average length of service (Years) | — | — | — | — | — | — | 
                                                18.1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Average annual salary | — | — | — | — | — | — | 
                                                6,219,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — |