Key Financial Data Of Reporting Company
| Concept | As at 2023-12-31 | 2023-10-01 to 2023-12-31 | As at 2023-09-30 | 2022-10-01 to 2023-09-30 | As at 2022-12-31 | 2022-10-01 to 2022-12-31 | 
|---|---|---|---|---|---|---|
| Key financial data of reporting company | ||||||
| Business results of reporting company | ||||||
| Net sales | — | 
                                                2,222,481,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                7,257,075,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,076,450,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Ordinary profit (loss) | — | 
                                                215,115,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                181,019,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                149,187,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets | 
                                                1,758,203,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,584,792,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,530,680,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Total assets | 
                                                4,813,723,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,582,566,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,598,747,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Basic earnings (loss) per share | — | 
                                                20.54
                                                
                                             | — | 
                                                12.24
                                                
                                             | — | 
                                                12.99
                                                
                                             | 
| Diluted earnings per share | — | 
                                                20.53
                                                
                                             | — | 
                                                12.22
                                                
                                             | — | 
                                                12.97
                                                
                                             | 
| Equity-to-asset ratio | 
                                                0.354
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.334
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.321
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — |