Consolidated Statement Of Cash Flows
| Concept | As at 2024-09-30 | 2024-04-01 to 2024-09-30 | As at 2024-03-31 | As at 2023-09-30 | 2023-04-01 to 2023-09-30 | As at 2023-03-31 | 
|---|---|---|---|---|---|---|
| Consolidated statement of cash flows | ||||||
| Statement of cash flows | ||||||
| Cash flows from operating activities | ||||||
| Profit (loss) before income taxes | — | 
                                                241,255,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                71,933,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Depreciation | — | 
                                                234,502,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                225,951,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Interest and dividend income | — | 
                                                -32,729,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -27,814,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Interest expenses | — | 
                                                5,613,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                4,348,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Increase (decrease) in retirement benefit liability | — | 
                                                25,447,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                15,233,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Increase (decrease) in provision for bonuses | — | 
                                                -1,957,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -5,219,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Loss (gain) on sale of property, plant and equipment | — | 
                                                -766,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -29,207,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Decrease (increase) in trade receivables | — | 
                                                145,298,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -375,142,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Subtotal | — | 
                                                554,692,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -812,241,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Income taxes paid | — | 
                                                -29,401,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -10,224,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Decrease (increase) in inventories | — | 
                                                -222,106,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -273,152,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Increase (decrease) in trade payables | — | 
                                                3,090,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                22,075,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) operating activities | — | 
                                                654,707,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -873,920,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Other, net | — | 
                                                48,061,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -50,885,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Interest and dividends received | — | 
                                                33,329,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                28,414,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Interest paid | — | 
                                                -5,371,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -4,328,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash flows from investing activities | ||||||
| Purchase of property, plant and equipment | — | 
                                                -519,551,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -494,670,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Proceeds from sale of property, plant and equipment | — | 
                                                2,061,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                38,779,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) investing activities | — | 
                                                -310,106,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -614,094,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Purchase of investment securities | — | 
                                                -10,848,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -2,887,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Proceeds from sale of investment securities | — | 
                                                214,650,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Other, net | — | 
                                                3,581,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -4,996,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash flows from financing activities | ||||||
| Proceeds from short-term borrowings | — | 
                                                100,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Purchase of treasury shares | — | 
                                                -23,076,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -54,319,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Dividends paid | — | 
                                                -31,518,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -31,927,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Repayments of long-term borrowings | — | 
                                                -18,400,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -18,400,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) financing activities | — | 
                                                39,474,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -80,268,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Effect of exchange rate change on cash and cash equivalents | — | 
                                                -13,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                130,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net increase (decrease) in cash and cash equivalents | — | 
                                                384,060,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -1,568,152,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | 
                                                3,096,757,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,712,696,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,844,222,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,412,374,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             |