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 | 2024-04-01 to 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 | — | — | — | — | — | 
                                                94,035,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                93,934,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                71,955,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                72,044,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                72,886,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                72,984,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                75,946,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                76,034,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                73,929,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                74,979,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Ordinary profit (loss) | — | — | — | — | — | 
                                                21,279,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                22,766,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                10,220,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                9,951,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                8,930,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                8,727,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                17,866,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                17,542,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                18,178,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                18,222,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) | — | — | — | — | — | — | — | 
                                                16,449,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                8,483,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                6,765,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                9,897,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                13,376,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Share capital | — | — | — | — | — | — | 
                                                23,853,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                23,853,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                23,853,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                23,853,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                23,853,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total number of issued shares | — | — | — | — | — | — | 
                                                45,939,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | — | 
                                                45,939,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
                                                45,939,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | — | — | 
                                                45,939,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | 
                                                45,939,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
| Net assets | — | — | — | — | 
                                                152,634,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                153,484,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                143,755,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                143,319,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                136,563,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                136,836,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                138,325,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                136,590,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                136,257,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                134,954,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | — | — | — | — | 
                                                190,422,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                189,474,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                171,623,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                168,853,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                163,747,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                166,328,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                165,181,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                161,798,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                163,332,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                162,327,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets per share | — | — | — | — | 
                                                3,974.47
                                                
                                             | — | 
                                                3,996.60
                                                
                                             | — | — | — | 
                                                3,796.05
                                                
                                             | 
                                                3,784.55
                                                
                                             | — | 
                                                3,644.33
                                                
                                             | 
                                                3,636.17
                                                
                                             | — | — | — | 
                                                3,642.34
                                                
                                             | 
                                                3,611.75
                                                
                                             | 
                                                3,555.93
                                                
                                             | — | — | 
                                                3,521.92
                                                
                                             | 
| Dividend paid per share | — | — | — | — | — | — | — | 
                                                190.00
                                                
                                             | 
                                                150.00
                                                
                                             | — | — | — | 
                                                150.00
                                                
                                             | — | — | — | 
                                                150.00
                                                
                                             | — | — | — | — | 
                                                150.00
                                                
                                             | — | — | 
| Interim dividend paid per share | — | — | — | — | — | — | — | 
                                                115.00
                                                
                                             | 
                                                75.00
                                                
                                             | — | — | — | 
                                                75.00
                                                
                                             | — | — | — | 
                                                75.00
                                                
                                             | — | — | — | — | 
                                                75.00
                                                
                                             | — | — | 
| Basic earnings (loss) per share | — | — | — | — | — | 
                                                365.42
                                                
                                             | — | 
                                                431.06
                                                
                                             | 
                                                224.79
                                                
                                             | 
                                                212.67
                                                
                                             | — | — | 
                                                180.07
                                                
                                             | — | — | 
                                                144.80
                                                
                                             | 
                                                260.61
                                                
                                             | 
                                                251.43
                                                
                                             | — | — | — | 
                                                346.63
                                                
                                             | 
                                                347.37
                                                
                                             | — | 
| Diluted earnings per share | — | — | — | — | — |  | — |  |  |  | — | — |  | — | — |  |  |  | — | — | — |  |  | — | 
| Equity-to-asset ratio | — | — | — | — | 
                                                0.802
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.810
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.838
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.849
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.834
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.819
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.834
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.844
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.834
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.831
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Rate of return on equity | — | — | — | — | — | 
                                                0.094
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.111
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.061
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.057
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.050
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.040
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.073
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.070
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.101
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.101
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Price-earnings ratio | — | — | — | — | — | 
                                                12.3
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                10.4
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                15.4
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                16.3
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                20.5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                25.5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                14.9
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                15.5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                12.5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                12.5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Payout ratio | — | — | — | — | — | — | — | 
                                                0.441
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.667
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.833
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.576
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.433
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
| Net cash provided by (used in) operating activities | — | — | — | — | — | 
                                                29,780,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                2,577,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                9,253,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                13,336,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                14,380,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) investing activities | — | — | — | — | — | 
                                                -19,650,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -5,854,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                -2,627,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -7,888,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -1,644,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) financing activities | — | — | — | — | — | 
                                                -5,369,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -5,658,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                -6,990,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -8,129,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -8,752,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | — | — | — | — | 
                                                70,085,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                65,325,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                74,260,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                74,625,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                77,305,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Number of employees | 
                                                1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,125
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,102
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,126
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1,103
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1,135
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,124
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1,117
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,130
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1,164
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,152
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,215
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                1,207
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                171
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                168
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                171
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                168
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                173
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                172
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                192
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                194
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                213
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                211
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                225
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                224
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total shareholder return | — | — | — | — | — | — | 
                                                1.048
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.807
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.824
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                0.833
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.892
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total return on share price index | — | — | — | — | — | — | 
                                                2.134
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                2.168
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.534
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1.450
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.421
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             |