Key Financial Data Of Reporting Company
| Concept | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | 2024-04-01 to 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | 2024-04-01 to 2025-03-31 | 2023-04-01 to 2024-03-31 | 2023-04-01 to 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | 2022-04-01 to 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | 2022-04-01 to 2023-03-31 | 2021-04-01 to 2022-03-31 | 2021-04-01 to 2022-03-31 | As at 2022-03-31 | As at 2022-03-31 | As at 2021-03-31 | 2020-04-01 to 2021-03-31 | 2020-04-01 to 2021-03-31 | As at 2021-03-31 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Key financial data of reporting company | ||||||||||||||||||||||||||||||
| Business results of reporting company | ||||||||||||||||||||||||||||||
| Net sales | — | — | — | — | — | — | — | — | — | — | 
                                                26,073,037,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                23,547,820,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                23,638,074,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                25,070,067,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                20,942,538,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                22,627,321,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                24,294,305,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                25,957,620,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                26,191,835,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                27,798,445,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Ordinary profit (loss) | — | — | — | — | — | — | — | — | — | — | 
                                                1,459,789,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,215,934,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,570,402,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,720,894,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,117,822,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,396,120,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,302,250,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,599,708,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                3,087,937,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,395,995,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                843,377,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,082,459,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                875,659,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,651,645,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                2,128,961,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Share capital | — | — | — | — | — | — | — | — | — | — | — | 
                                                565,295,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                565,295,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                565,295,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                565,295,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                565,295,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total number of issued shares | — | — | — | — | — | — | — | — | — | — | — | 
                                                7,378,050
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | — | — | 
                                                7,378,050
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
                                                7,378,050
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | — | — | 
                                                7,378,050
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | 
                                                7,378,050
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
| Net assets | — | — | — | — | — | — | — | — | 
                                                21,249,703,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                19,345,370,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                20,616,433,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                18,911,320,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                18,062,993,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                19,556,474,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                19,162,081,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                17,827,185,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                18,108,816,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                16,975,287,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | — | — | — | — | — | — | — | — | 
                                                28,841,139,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                25,443,051,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                29,618,535,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                26,830,328,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                23,594,371,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                26,191,190,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                26,208,966,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                23,787,397,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                26,555,879,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                24,895,132,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets per share | — | — | — | — | — | — | — | — | 
                                                2,887.37
                                                
                                             | — | — | 
                                                2,628.61
                                                
                                             | — | — | — | — | 
                                                2,801.32
                                                
                                             | 
                                                2,569.63
                                                
                                             | — | 
                                                2,454.37
                                                
                                             | 
                                                2,657.30
                                                
                                             | — | — | — | 
                                                2,601.32
                                                
                                             | 
                                                2,422.32
                                                
                                             | 
                                                2,458.84
                                                
                                             | — | — | 
                                                2,306.57
                                                
                                             | 
| Dividend paid per share | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                65.00
                                                
                                             | 
                                                60.00
                                                
                                             | — | — | — | 
                                                50.00
                                                
                                             | — | — | — | 
                                                70.00
                                                
                                             | — | — | — | — | 
                                                80.00
                                                
                                             | — | — | 
| Interim dividend paid per share | — | — | — | — | — | — | — | — | — | — | — | — | — |  |  | — | — | — |  | — | — | — |  | — | — | — | — |  | — | — | 
| Basic earnings (loss) per share | — | — | — | — | — | — | — | — | — | — | 
                                                135.53
                                                
                                             | — | — | 
                                                114.60
                                                
                                             | 
                                                147.08
                                                
                                             | 
                                                159.93
                                                
                                             | — | — | 
                                                118.98
                                                
                                             | — | — | 
                                                142.95
                                                
                                             | 
                                                224.42
                                                
                                             | 
                                                250.11
                                                
                                             | — | — | — | 
                                                289.28
                                                
                                             | 
                                                313.43
                                                
                                             | — | 
| Diluted earnings per share | — | — | — | — | — | — | — | — | — | — |  | — | — |  |  |  | — | — |  | — | — |  |  |  | — | — | — |  |  | — | 
| Equity-to-asset ratio | — | — | — | — | — | — | — | — | 
                                                0.737
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.760
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.696
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.705
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.766
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.747
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.730
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.749
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.681
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.682
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Rate of return on equity | — | — | — | — | — | — | — | — | — | — | 
                                                0.0476
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.0441
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.0586
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.0586
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.0488
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.0544
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.0949
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.0989
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.1333
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.1359
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Price-earnings ratio | — | — | — | — | — | — | — | — | — | — | 
                                                9.86
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                11.67
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                10.19
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                9.37
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                10.82
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                9.00
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                8.11
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                7.28
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                7.26
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                6.70
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Payout ratio | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                0.5672
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.4079
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.4202
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.3119
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.2765
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
| Net cash provided by (used in) operating activities | — | — | — | — | — | — | — | — | — | — | 
                                                -85,457,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                3,514,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                3,750,435,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,044,293,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                583,966,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) investing activities | — | — | — | — | — | — | — | — | — | — | 
                                                -429,002,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -263,904,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                -958,119,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -1,020,835,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -465,914,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) financing activities | — | — | — | — | — | — | — | — | — | — | 
                                                -446,250,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -371,544,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                -520,896,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -693,595,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -612,157,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | — | — | — | — | — | — | — | — | 
                                                4,399,150,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                5,359,860,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                5,989,929,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                3,726,359,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,382,857,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Number of employees | 
                                                40
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                103
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                83
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                105
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                79
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                105
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                40
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                248
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                327
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                228
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                307
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                79
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                312
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                293
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                288
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                304
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                293
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                271
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                286
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                263
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total shareholder return | — | — | — | — | — | — | — | — | — | — | — | 
                                                0.989
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1.047
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.885
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1.173
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.298
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total return on share price index | — | — | — | — | — | — | — | — | — | — | — | 
                                                1.895
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1.973
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.428
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1.387
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.393
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             |