Key Financial Data Of Reporting Company
| Concept | 2023-04-01 to 2023-09-30 | As at 2023-09-30 | 2023-07-01 to 2023-09-30 | As at 2023-03-31 | 2022-04-01 to 2023-03-31 | 2022-04-01 to 2022-09-30 | As at 2022-09-30 | 2022-07-01 to 2022-09-30 | 
|---|---|---|---|---|---|---|---|---|
| Key financial data of reporting company | ||||||||
| Business results of reporting company | ||||||||
| Net sales | 
                                                2,487,995,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                4,923,246,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,512,662,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Ordinary profit (loss) | 
                                                525,104,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                853,968,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                527,009,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Profit (loss) | 
                                                370,062,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                568,174,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                358,915,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Equity in earnings (losses) of affiliates if equity method is applied | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Share capital | — | 
                                                831,413,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                831,413,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                831,413,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Total number of issued shares | — | 
                                                4,558,860
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
                                                4,558,860
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | 
                                                4,558,860
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
| Net assets | — | 
                                                5,955,317,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,669,839,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                5,447,518,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Total assets | — | 
                                                8,139,682,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                8,115,854,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                7,814,940,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Dividend paid per share |  | — | — | — | 
                                                25.00
                                                
                                             |  | — | — | 
| Basic earnings (loss) per share | 
                                                88.66
                                                
                                             | — | 
                                                54.18
                                                
                                             | — | 
                                                136.13
                                                
                                             | 
                                                85.99
                                                
                                             | — | 
                                                37.71
                                                
                                             | 
| Diluted earnings per share |  | — | — | — |  |  | — | — | 
| Equity-to-asset ratio | — | 
                                                0.732
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.699
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.697
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) operating activities | 
                                                16,516,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                544,510,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                285,918,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Net cash provided by (used in) investing activities | 
                                                -66,374,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -10,328,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -4,996,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Net cash provided by (used in) financing activities | 
                                                -182,250,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -191,136,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -130,522,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Cash and cash equivalents | — | 
                                                2,448,963,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,679,848,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                2,487,958,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — |