Key Financial Data Of Reporting Company
| Concept | As at 2024-09-30 | 2023-10-01 to 2024-09-30 | As at 2024-09-30 | 2023-10-01 to 2024-09-30 | As at 2023-09-30 | 2022-10-01 to 2023-09-30 | As at 2023-09-30 | 2022-10-01 to 2023-09-30 | 2021-10-01 to 2022-09-30 | As at 2022-09-30 | As at 2022-09-30 | 2021-10-01 to 2022-09-30 | As at 2021-09-30 | 2020-10-01 to 2021-09-30 | As at 2021-09-30 | 2020-10-01 to 2021-09-30 | 2019-10-01 to 2020-09-30 | As at 2020-09-30 | As at 2020-09-30 | 2019-10-01 to 2020-09-30 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Key financial data of reporting company | ||||||||||||||||||||
| Business results of reporting company | ||||||||||||||||||||
| Net sales | — | 
                                                3,609,812,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,386,896,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,689,513,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,516,848,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,759,012,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                4,465,205,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,582,898,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,068,678,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,202,787,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                3,580,823,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Ordinary profit (loss) | — | 
                                                114,592,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                207,396,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                157,523,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                298,610,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                188,463,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                258,316,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                188,352,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                228,431,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                37,058,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                58,135,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Profit (loss) | — | 
                                                166,936,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                59,634,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                158,193,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                155,068,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -26,747,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Share capital | — | — | 
                                                468,134,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                468,134,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                468,134,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                468,134,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                468,134,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Total number of issued shares | — | — | 
                                                2,323,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
                                                2,323,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | — | 
                                                2,323,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | 
                                                2,323,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | — | 
                                                2,323,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | 
| Net assets | 
                                                4,276,130,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,678,915,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,554,633,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,158,171,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                3,533,984,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,018,132,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,410,461,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,701,142,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                3,264,270,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,487,786,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Total assets | 
                                                5,909,786,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,220,416,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,118,850,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,762,579,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                5,372,045,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,928,044,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,389,608,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,732,237,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                4,858,902,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,136,483,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net assets per share | 
                                                1,840.97
                                                
                                             | — | 
                                                1,583.86
                                                
                                             | — | 
                                                1,530.35
                                                
                                             | — | 
                                                1,790.19
                                                
                                             | — | — | 
                                                1,521.46
                                                
                                             | 
                                                1,729.90
                                                
                                             | — | 
                                                1,468.28
                                                
                                             | — | 
                                                1,593.43
                                                
                                             | — | — | 
                                                1,405.34
                                                
                                             | 
                                                1,501.57
                                                
                                             | — | 
| Dividend paid per share | — | 
                                                20.00
                                                
                                             | — | — | — | 
                                                20.00
                                                
                                             | — | — | 
                                                20.00
                                                
                                             | — | — | — | — | 
                                                15.00
                                                
                                             | — | — | 
                                                5.00
                                                
                                             | — | — | — | 
| Interim dividend paid per share | — |  | — | — | — |  | — | — |  | — | — | — | — |  | — | — |  | — | — | — | 
| Basic earnings (loss) per share | — | 
                                                71.87
                                                
                                             | — | 
                                                78.44
                                                
                                             | — | 
                                                25.67
                                                
                                             | — | 
                                                67.51
                                                
                                             | 
                                                68.11
                                                
                                             | — | — | 
                                                92.49
                                                
                                             | — | 
                                                66.76
                                                
                                             | — | 
                                                85.00
                                                
                                             | 
                                                -11.52
                                                
                                             | — | — | 
                                                -11.38
                                                
                                             | 
| Diluted earnings per share | — |  | — |  | — |  | — |  |  | — | — |  | — |  | — |  |  | — | — |  | 
| Equity-to-asset ratio | 
                                                0.724
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.705
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.694
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.722
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.658
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.678
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.633
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.646
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.672
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.679
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Rate of return on equity | — | 
                                                0.046
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.043
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.017
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.038
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.046
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.056
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.046
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.055
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Price-earnings ratio | — | 
                                                10.0
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                9.1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                34.3
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                13.0
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                10.4
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                7.7
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                12.7
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                10.0
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Payout ratio | — | 
                                                0.278
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.779
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.294
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.225
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
| Net cash provided by (used in) operating activities | — | — | — | 
                                                374,083,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                348,238,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                126,751,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                280,281,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                227,884,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net cash provided by (used in) investing activities | — | — | — | 
                                                -94,237,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -103,602,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -49,091,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -113,917,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -209,460,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net cash provided by (used in) financing activities | — | — | — | 
                                                -30,131,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -286,780,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -32,567,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                49,755,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -10,674,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Cash and cash equivalents | 
                                                2,052,891,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1,820,016,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,838,528,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,727,336,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,493,232,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Number of employees | 
                                                157
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                145
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                152
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                165
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                148
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                162
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                157
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                173
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                159
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                176
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Average number of temporary employees | 
                                                21
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                20
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                19
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                20
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                18
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                19
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                18
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                18
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                25
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                25
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Total shareholder return | — | — | 
                                                0.777
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.918
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.733
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.846
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                1.031
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
| Total return on share price index | — | — | 
                                                1.879
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.612
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                1.242
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                1.337
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                1.049
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — |