Key Financial Data Of Reporting Company
| Concept | As at 2024-03-31 | 2023-04-01 to 2024-03-31 | As at 2023-03-31 | 2022-04-01 to 2023-03-31 | 2021-04-01 to 2022-03-31 | As at 2022-03-31 | 2020-04-01 to 2021-03-31 | As at 2021-03-31 | As at 2020-03-31 | 2019-04-01 to 2020-03-31 | 
|---|---|---|---|---|---|---|---|---|---|---|
| Key financial data of reporting company | ||||||||||
| Business results of reporting company | ||||||||||
| Net sales | — | 
                                                5,888,372,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                6,020,260,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,401,608,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,117,472,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                6,013,290,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Ordinary profit (loss) | — | 
                                                256,940,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                310,574,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                295,642,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                197,788,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                242,367,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Profit (loss) | — | 
                                                183,941,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                252,477,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                186,199,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                321,559,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                165,977,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Equity in earnings (losses) of affiliates if equity method is applied | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Share capital | 
                                                664,740,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                664,740,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                664,740,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                664,740,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                664,740,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Total number of issued shares | 
                                                4,022,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
                                                4,022,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | 
                                                4,022,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
                                                4,022,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                4,022,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
| Net assets | 
                                                3,147,880,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,012,504,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                2,808,772,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,654,547,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,364,842,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Total assets | 
                                                5,762,421,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                6,062,236,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                5,717,321,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,849,470,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,907,262,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net assets per share | 
                                                834.63
                                                
                                             | — | 
                                                801.46
                                                
                                             | — | — | 
                                                750.57
                                                
                                             | — | 
                                                712.71
                                                
                                             | 
                                                634.92
                                                
                                             | — | 
| Dividend paid per share | — | 
                                                16.0
                                                
                                             | — | 
                                                16.0
                                                
                                             | 
                                                15.0
                                                
                                             | — | 
                                                10.0
                                                
                                             | — | — | 
                                                10.0
                                                
                                             | 
| Interim dividend paid per share | — |  | — |  |  | — |  | — | — |  | 
| Basic earnings (loss) per share | — | 
                                                48.82
                                                
                                             | — | 
                                                67.27
                                                
                                             | 
                                                49.87
                                                
                                             | — | 
                                                86.33
                                                
                                             | — | — | 
                                                44.56
                                                
                                             | 
| Diluted earnings per share | — |  | — |  |  | — |  | — | — |  | 
| Equity-to-asset ratio | 
                                                0.546
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.497
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.491
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.454
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.400
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Rate of return on equity | — | 
                                                0.060
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.087
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.068
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.128
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.072
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Price-earnings ratio | — | 
                                                10.6
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                7.0
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                9.0
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                4.6
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                7.6
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Payout ratio | — | 
                                                0.328
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.238
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.301
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.116
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.224
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Net cash provided by (used in) operating activities | — | 
                                                -223,251,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -213,867,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                269,301,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                344,150,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -109,579,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net cash provided by (used in) investing activities | — | 
                                                -144,391,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -125,427,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -128,594,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                207,710,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -211,053,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net cash provided by (used in) financing activities | — | 
                                                338,155,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                384,409,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -362,716,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -219,189,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                315,312,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Cash and cash equivalents | 
                                                478,597,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                508,084,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                462,970,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                684,979,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                352,308,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Number of employees | 
                                                260
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                264
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                270
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                274
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                272
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Average number of temporary employees | 
                                                74
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                57
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                44
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                54
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                58
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Total shareholder return | 
                                                1.429
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.276
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                1.185
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.024
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.851
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Total return on share price index | 
                                                1.962
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.388
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                1.312
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.286
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.905
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — |