Key Financial Data Of Reporting Company
| Concept | 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 | As at 2025-03-31 | As at 2024-03-31 | 2023-04-01 to 2024-03-31 | As at 2023-03-31 | 2022-04-01 to 2023-03-31 | 2021-04-01 to 2022-03-31 | As at 2022-03-31 | As at 2021-03-31 | 2020-04-01 to 2021-03-31 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Key financial data of reporting company | ||||||||||||||
| Business results of reporting company | ||||||||||||||
| Net sales | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                13,237,395,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Revenue | — | — | 
                                                10,020,947,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                10,143,154,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                9,960,242,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                9,676,056,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Ordinary profit (loss) | — | — | 
                                                1,027,873,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                795,796,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                621,019,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                754,246,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,460,018,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Profit (loss) | — | — | 
                                                725,806,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                401,909,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                82,316,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                391,698,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                984,297,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Equity in earnings (losses) of affiliates if equity method is applied | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Share capital | — | — | — | 
                                                923,761,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                923,761,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                923,761,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                923,761,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                153,236,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Total number of issued shares | — | — | — | 
                                                4,720,245
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | 
                                                4,720,245
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
                                                4,720,245
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | 
                                                4,720,245
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                3,887,245
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
| Net assets | — | — | — | 
                                                7,864,042,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                7,419,776,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                7,292,198,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                7,490,993,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,031,800,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Total assets | — | — | — | 
                                                14,461,382,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                13,950,101,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                13,762,244,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                13,512,765,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                12,778,823,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net assets per share | — | — | — | 
                                                1,666.05
                                                
                                             | — | — | 
                                                1,571.93
                                                
                                             | — | 
                                                1,544.89
                                                
                                             | — | — | 
                                                1,587.01
                                                
                                             | 
                                                1,551.69
                                                
                                             | — | 
| Dividend paid per share | — | — | 
                                                61.00
                                                
                                             | — | — | — | — | 
                                                60.00
                                                
                                             | — | 
                                                60.00
                                                
                                             | 
                                                60.00
                                                
                                             | — | — | 
                                                60.00
                                                
                                             | 
| Interim dividend paid per share | — | — | 
                                                30.00
                                                
                                             | — | — | — | — | 
                                                30.00
                                                
                                             | — | 
                                                30.00
                                                
                                             | 
                                                30.00
                                                
                                             | — | — |  | 
| Basic earnings (loss) per share | — | — | 
                                                153.77
                                                
                                             | — | — | — | — | 
                                                85.15
                                                
                                             | — | 
                                                17.44
                                                
                                             | 
                                                83.46
                                                
                                             | — | — | 
                                                253.21
                                                
                                             | 
| Diluted earnings per share | — | — |  | — | — | — | — |  | — |  |  | — | — |  | 
| Equity-to-asset ratio | — | — | — | 
                                                0.544
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.532
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.530
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.554
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.472
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Rate of return on equity | — | — | 
                                                0.095
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.055
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.011
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.058
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.176
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Price-earnings ratio | — | — | 
                                                10.41
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                17.80
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                76.26
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                15.11
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Payout ratio | — | — | 
                                                0.397
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.705
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                3.440
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.719
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.237
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Net cash provided by (used in) operating activities | — | — | 
                                                1,742,029,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                1,191,479,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,339,174,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                515,072,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                2,434,323,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net cash provided by (used in) investing activities | — | — | 
                                                -2,147,049,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -523,035,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -2,010,311,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -2,206,702,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -653,233,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net cash provided by (used in) financing activities | — | — | 
                                                -287,804,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -286,137,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -285,944,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,118,868,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -178,796,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Cash and cash equivalents | — | — | — | 
                                                3,406,571,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                4,099,395,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,717,088,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                4,674,169,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,246,931,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Number of employees | 
                                                177
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                217
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                443
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                26
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                23
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                447
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                457
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                456
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                445
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Average number of temporary employees | 
                                                1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                84
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                85
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                87
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                102
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                92
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                96
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Total shareholder return | — | — | — | 
                                                1.413
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                1.296
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.103
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Total return on share price index | — | — | — | 
                                                1.472
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                1.496
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.058
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — |