Key Financial Data Of Group
| Concept | As at 2023-12-31 | 2023-10-01 to 2023-12-31 | 2023-04-01 to 2023-12-31 | As at 2023-03-31 | 2022-04-01 to 2023-03-31 | As at 2022-12-31 | 2022-04-01 to 2022-12-31 | 2022-10-01 to 2022-12-31 | 
|---|---|---|---|---|---|---|---|---|
| Key financial data of group | ||||||||
| Business results of group | ||||||||
| Net sales | — | — | 
                                                3,790,190,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,923,246,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,728,853,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Ordinary profit (loss) | — | — | 
                                                811,223,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                853,968,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                722,440,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net assets | 
                                                6,182,782,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                5,669,839,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,596,646,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Total assets | 
                                                8,387,601,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                8,115,854,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                8,089,253,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Basic earnings (loss) per share | — | 
                                                49.38
                                                
                                             | 
                                                138.01
                                                
                                             | — | 
                                                136.13
                                                
                                             | — | 
                                                119.24
                                                
                                             | 
                                                33.24
                                                
                                             | 
| Diluted earnings per share | — | — |  | — |  | — |  | — | 
| Equity-to-asset ratio | 
                                                0.737
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.699
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.692
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — |