Employees
| Concept | As at 2024-09-30 | As at 2024-09-30 | As at 2023-09-30 | As at 2023-09-30 | As at 2022-09-30 | As at 2022-09-30 | As at 2021-09-30 | As at 2021-09-30 | As at 2020-09-30 | As at 2020-09-30 | 
|---|---|---|---|---|---|---|---|---|---|---|
| Employees | ||||||||||
| Information about reporting company | ||||||||||
| Information about employees of reporting company | ||||||||||
| Number of employees | 
                                                317
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                252
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                308
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                252
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                266
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                218
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                234
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                197
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                216
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                250
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                66
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                57
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                69
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                53
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                85
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                76
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                80
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                74
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                75
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                76
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average age (Years) | — | 
                                                29
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Average length of service (Years) | — | 
                                                1.7
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Average annual salary | — | 
                                                4,459,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — |