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 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 2021-03-31 | 
|---|---|---|---|---|---|---|---|---|---|---|---|
| Employees | |||||||||||
| Information about reporting company | |||||||||||
| Information about employees of reporting company | |||||||||||
| Number of employees | 
                                                74
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                72
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                150
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                224
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                72
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                64
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                258
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                214
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                71
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                62
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                48
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
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                                                        xbrli:pure
                                                    
                                                
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                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average age (Years) | — | — | — | — | 
                                                42.3
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | 
| Average length of service (Years) | — | — | — | — | 
                                                2.5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | 
| Average annual salary | — | — | — | — | 
                                                9,170,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — |