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 | 
                                                7,227,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                13,192,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,323,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Ordinary profit (loss) | 
                                                763,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,173,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                554,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) | 
                                                550,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                583,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                466,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Equity in earnings (losses) of affiliates if equity method is applied | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Share capital | — | 
                                                1,789,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,789,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,789,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total number of issued shares | — | 
                                                10,839,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                10,839,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | 
                                                10,839,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
| Net assets | — | 
                                                20,254,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                19,897,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                20,046,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | — | 
                                                26,818,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                27,223,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                28,275,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Dividend paid per share | 
                                                6.00
                                                
                                             | — | — | 
                                                12.00
                                                
                                             | 
                                                6.00
                                                
                                             | — | 
| Basic earnings (loss) per share | 
                                                60.02
                                                
                                             | — | — | 
                                                61.50
                                                
                                             | 
                                                48.95
                                                
                                             | — | 
| Diluted earnings per share |  | — | — |  |  | — | 
| Equity-to-asset ratio | — | 
                                                0.7552
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.7309
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.7090
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Net cash provided by (used in) operating activities | 
                                                1,692,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                767,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -442,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) investing activities | 
                                                -401,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                76,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                172,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) financing activities | 
                                                -925,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -2,197,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -990,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | — | 
                                                5,455,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,265,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                5,330,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             |