Key Financial Data Of Group
| Concept | As at 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | 2024-01-01 to 2024-12-31 | 2024-01-01 to 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | 2023-01-01 to 2023-12-31 | As at 2023-12-31 | 2023-01-01 to 2023-12-31 | As at 2023-12-31 | As at 2022-12-31 | 2022-01-01 to 2022-12-31 | As at 2022-12-31 | 2022-01-01 to 2022-12-31 | 2021-01-01 to 2021-12-31 | As at 2021-12-31 | As at 2021-12-31 | 2021-01-01 to 2021-12-31 | 2020-01-01 to 2020-12-31 | As at 2020-12-31 | 2020-01-01 to 2020-12-31 | As at 2020-12-31 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Key financial data of group | ||||||||||||||||||||||||||||
| Business results of group | ||||||||||||||||||||||||||||
| Net sales | — | — | — | — | — | — | — | 
                                                4,236,549,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,607,016,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                5,059,763,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,946,996,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                4,818,253,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,855,714,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,898,333,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                4,696,287,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,380,607,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,850,113,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Ordinary profit (loss) | — | — | — | — | — | — | — | 
                                                277,111,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                441,109,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                425,896,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                135,006,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                216,976,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                56,793,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                473,262,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                370,884,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                465,438,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                554,754,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) attributable to owners of parent | — | — | — | — | — | — | — | — | 
                                                327,110,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                626,528,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                359,247,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                658,101,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                438,081,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Comprehensive income | — | — | — | — | — | — | — | — | 
                                                244,516,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                563,201,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -368,464,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1,044,536,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,372,237,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Net assets | — | — | — | — | — | 
                                                3,458,699,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                4,645,339,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,677,929,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,757,845,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,391,458,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,846,188,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                4,730,522,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,050,636,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                4,186,949,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,273,458,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | — | — | — | — | — | 
                                                4,409,513,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                5,822,328,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,602,471,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,424,368,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,077,822,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,347,800,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                5,966,777,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,377,131,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                5,176,143,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,401,859,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets per share | — | — | — | — | — | 
                                                386.58
                                                
                                             | — | — | — | — | — | 
                                                519.21
                                                
                                             | — | 
                                                523.49
                                                
                                             | — | 
                                                420.53
                                                
                                             | 
                                                492.11
                                                
                                             | — | 
                                                431.01
                                                
                                             | — | — | 
                                                530.81
                                                
                                             | 
                                                566.73
                                                
                                             | — | — | 
                                                469.81
                                                
                                             | — | 
                                                479.52
                                                
                                             | 
| Basic earnings (loss) per share | — | — | — | — | — | — | — | 
                                                21.35
                                                
                                             | 
                                                36.58
                                                
                                             | — | — | — | 
                                                70.14
                                                
                                             | — | 
                                                33.90
                                                
                                             | — | — | 
                                                40.28
                                                
                                             | — | 
                                                23.97
                                                
                                             | 
                                                58.12
                                                
                                             | — | — | 
                                                73.85
                                                
                                             | 
                                                49.16
                                                
                                             | — | 
                                                59.35
                                                
                                             | — | 
| Diluted earnings per share | — | — | — | — | — | — | — |  |  | — | — | — |  | — |  | — | — |  | — |  |  | — | — |  |  | — |  | — | 
| Equity-to-asset ratio | — | — | — | — | — | 
                                                0.784
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                0.798
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.835
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.849
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.865
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.885
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.793
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.792
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.809
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.791
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Rate of return on equity | — | — | — | — | — | — | — | 
                                                0.053
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.070
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.138
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.080
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.076
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.050
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.116
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.141
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.118
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.148
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Price-earnings ratio | — | — | — | — | — | — | — | 
                                                36.4
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                21.3
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                12.6
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                26.0
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                17.5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                29.3
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                13.5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                10.6
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                19.8
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                16.4
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) operating activities | — | — | — | — | — | — | — | — | 
                                                321,772,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                465,720,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -167,992,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                230,046,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                513,021,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Net cash provided by (used in) investing activities | — | — | — | — | — | — | — | — | 
                                                -395,355,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                303,143,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -330,107,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                483,384,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -411,755,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Net cash provided by (used in) financing activities | — | — | — | — | — | — | — | — | 
                                                213,914,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -325,340,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -298,672,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                -267,437,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -267,748,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Cash and cash equivalents | — | — | — | — | — | — | — | — | — | — | — | 
                                                1,699,697,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,502,405,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,025,175,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1,794,683,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                1,321,127,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Number of employees | 
                                                39
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                125
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                173
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                343
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                337
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                35
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                125
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                40
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                543
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                540
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                329
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                629
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                320
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                310
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                613
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                309
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                590
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                4
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                175
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                36
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                36
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                215
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                12
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                175
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                4
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                227
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                239
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                229
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                204
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                198
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                153
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                156
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                150
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                153
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             |