Key Financial Data Of Group
| Concept | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | 2023-04-01 to 2024-03-31 | As at 2024-03-31 | 2023-04-01 to 2024-03-31 | As at 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 | 2019-04-01 to 2020-03-31 | As at 2020-03-31 | 2019-04-01 to 2020-03-31 | As at 2020-03-31 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Key financial data of group | ||||||||||||||||||||||||||
| Business results of group | ||||||||||||||||||||||||||
| Net sales | — | — | — | — | 
                                                14,686,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                18,489,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                13,227,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                17,024,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                13,014,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                17,222,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                14,523,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                18,155,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                16,058,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                20,539,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Ordinary profit (loss) | — | — | — | — | 
                                                124,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                203,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                12,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                14,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                153,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                303,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                267,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                347,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                301,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                370,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) attributable to owners of parent | — | — | — | — | — | — | 
                                                284,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                -326,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                198,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                232,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                251,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Comprehensive income | — | — | — | — | — | — | 
                                                319,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                -315,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                213,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                337,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                205,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net assets | — | — | — | — | — | — | — | 
                                                5,476,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,892,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,643,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,157,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                5,560,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,970,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,453,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                4,973,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,231,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,883,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | — | — | — | — | — | — | — | 
                                                11,661,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                10,599,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                9,695,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                10,675,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                10,941,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                9,635,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                11,291,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                10,207,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                11,800,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                10,861,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets per share | — | — | — | — | — | — | — | 
                                                1,565.58
                                                
                                             | — | 
                                                1,398.63
                                                
                                             | — | 
                                                1,327.27
                                                
                                             | 
                                                1,474.35
                                                
                                             | — | — | — | 
                                                1,589.49
                                                
                                             | 
                                                1,420.81
                                                
                                             | 
                                                1,558.94
                                                
                                             | — | — | 
                                                1,421.85
                                                
                                             | — | 
                                                1,495.46
                                                
                                             | — | 
                                                1,396.01
                                                
                                             | 
| Basic earnings (loss) per share | — | — | — | — | 
                                                63.71
                                                
                                             | — | 
                                                81.45
                                                
                                             | — | — | — | 
                                                -70.14
                                                
                                             | — | — | 
                                                -93.43
                                                
                                             | 
                                                28.29
                                                
                                             | 
                                                56.62
                                                
                                             | — | — | — | 
                                                56.51
                                                
                                             | 
                                                66.50
                                                
                                             | — | 
                                                64.44
                                                
                                             | — | 
                                                71.80
                                                
                                             | — | 
| Diluted earnings per share | — | — | — | — |  | — |  | — | — | — |  | — | — |  |  |  | — | — | — |  |  | — |  | — |  | — | 
| Equity-to-asset ratio | — | — | — | — | — | — | — | 
                                                0.4696
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.4616
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.4789
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.4831
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.5082
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.5158
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.4830
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.4873
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.4433
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.4496
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Rate of return on equity | — | — | — | — | 
                                                0.0467
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.0536
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                -0.0510
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                -0.0610
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.0199
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.0360
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.0401
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.0435
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.0467
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.0484
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Price-earnings ratio | — | — | — | — | 
                                                13.97
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                10.93
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                30.51
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                15.24
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                15.82
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                13.44
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                13.16
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                11.81
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) operating activities | — | — | — | — | — | — | 
                                                130,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                -805,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,037,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                829,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -109,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) investing activities | — | — | — | — | — | — | 
                                                -43,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                -205,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -168,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -73,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -181,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) financing activities | — | — | — | — | — | — | 
                                                -2,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                707,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -520,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -920,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                280,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | — | — | — | — | — | — | — | 
                                                1,059,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                975,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,278,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                929,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                1,093,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Number of employees | 
                                                57
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                164
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                401
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                57
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                121
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                622
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                251
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                429
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                441
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                639
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                642
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                441
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                648
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                450
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                626
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                416
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                17
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                99
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                113
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                17
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                69
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                229
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                60
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                146
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                156
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                231
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                244
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                162
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                246
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                163
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                262
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                163
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             |