Key Financial Data Of Reporting Company
| Concept | 2024-04-01 to 2024-09-30 | As at 2024-09-30 | As at 2024-03-31 | 2023-04-01 to 2024-03-31 | 2023-04-01 to 2023-09-30 | As at 2023-09-30 | 
|---|---|---|---|---|---|---|
| Key financial data of reporting company | ||||||
| Business results of reporting company | ||||||
| Net sales | 
                                                29,739,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                55,407,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                27,424,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Ordinary profit (loss) | 
                                                2,143,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,868,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,098,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) | 
                                                1,535,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,377,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                717,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Equity in earnings (losses) of affiliates if equity method is applied | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Share capital | — | 
                                                10,758,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                10,758,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                10,758,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total number of issued shares | — | 
                                                9,451,169
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                9,451,169
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | 
                                                9,451,169
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
| Net assets | — | 
                                                37,899,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                36,661,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                35,875,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | — | 
                                                75,999,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                75,802,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                76,274,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Dividend paid per share | 
                                                40.00
                                                
                                             | — | — | 
                                                70.00
                                                
                                             | 
                                                35.00
                                                
                                             | — | 
| Basic earnings (loss) per share | 
                                                179.75
                                                
                                             | — | — | 
                                                159.98
                                                
                                             | 
                                                82.18
                                                
                                             | — | 
| Diluted earnings per share |  | — | — |  |  | — | 
| Equity-to-asset ratio | — | 
                                                0.499
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.484
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.470
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Net cash provided by (used in) operating activities | 
                                                769,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                627,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -341,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) investing activities | 
                                                -1,749,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -3,536,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -1,422,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) financing activities | 
                                                477,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                14,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,272,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | — | 
                                                4,617,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,120,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                7,522,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             |