Employees
| Concept | As at 2025-02-28 | As at 2025-02-28 | As at 2025-02-28 | As at 2025-02-28 | As at 2025-02-28 | As at 2025-02-28 | As at 2024-02-29 | As at 2024-02-29 | As at 2023-02-28 | As at 2023-02-28 | As at 2022-02-28 | As at 2022-02-28 | As at 2021-02-28 | As at 2021-02-28 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Employees | ||||||||||||||
| Information about reporting company | ||||||||||||||
| Information about employees of reporting company | ||||||||||||||
| Number of employees | 
                                                30
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                232
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                222
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                257
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                211
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                238
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                252
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                230
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                186
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                215
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                137
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                114
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                3
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                6
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                8
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                8
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                7
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                13
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                18
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                11
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                8
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                14
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                19
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                13
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average age (Years) | — | 
                                                37.5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | 
| Average length of service (Years) | — | 
                                                3.1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | 
| Average annual salary | — | 
                                                6,361,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — |