Key Financial Data Of Group
| Concept | 2023-04-01 to 2023-12-31 | As at 2023-12-31 | 2023-10-01 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 | 
                                                6,947,881,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                8,376,142,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                6,216,758,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Ordinary profit (loss) | 
                                                220,262,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                131,369,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                101,905,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) attributable to owners of parent | 
                                                141,733,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                80,046,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                45,224,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Comprehensive income | 
                                                160,090,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                85,542,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                44,508,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net assets | — | 
                                                1,115,051,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                937,645,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                662,922,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Total assets | — | 
                                                5,357,872,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,767,123,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,708,217,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Basic earnings (loss) per share | 
                                                19.96
                                                
                                             | — | 
                                                21.26
                                                
                                             | — | 
                                                11.93
                                                
                                             | — | 
                                                6.78
                                                
                                             | 
                                                20.71
                                                
                                             | 
| Diluted earnings per share | 
                                                19.37
                                                
                                             | — | — | — | 
                                                11.41
                                                
                                             | — | 
                                                6.48
                                                
                                             | — | 
| Equity-to-asset ratio | — | 
                                                0.203
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.192
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.135
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — |