Consolidated Statement Of Cash Flows
| Concept | 2024-04-01 to 2025-03-31 | As at 2025-03-31 | 2024-04-01 to 2025-03-31 | 2023-04-01 to 2024-03-31 | As at 2024-03-31 | 2023-04-01 to 2024-03-31 | As at 2023-03-31 | 
|---|---|---|---|---|---|---|---|
| Consolidated statement of cash flows | |||||||
| Statement of cash flows | |||||||
| Cash flows from operating activities | |||||||
| Profit (loss) before income taxes | 
                                                1,340,759,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,392,003,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,015,642,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                995,540,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Depreciation | — | — | 
                                                624,309,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                607,227,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Increase (decrease) in allowance for doubtful accounts | — | — | 
                                                -2,075,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -132,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Interest and dividend income | — | — | 
                                                -4,327,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -2,604,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Interest expenses | — | — | 
                                                2,583,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,615,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Increase (decrease) in retirement benefit liability | — | — | 
                                                9,290,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -72,336,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Increase (decrease) in provision for bonuses | — | — | 
                                                841,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,900,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Share of loss (profit) of entities accounted for using equity method | — | — | 
                                                -15,133,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -9,932,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Loss (gain) on sale of property, plant and equipment | — | — | 
                                                -4,983,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -105,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Subtotal | — | — | 
                                                1,675,072,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,206,710,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Decrease (increase) in trade receivables | — | — | 
                                                -226,351,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -331,612,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Decrease (increase) in inventories | — | — | 
                                                -363,637,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -91,939,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Increase (decrease) in trade payables | — | — | 
                                                232,193,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -32,415,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Net cash provided by (used in) operating activities | — | — | 
                                                1,398,611,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,175,327,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Other, net | — | — | 
                                                13,746,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                36,140,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Interest and dividends received | — | — | 
                                                4,327,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,604,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Interest paid | — | — | 
                                                -2,650,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -3,734,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Cash flows from investing activities | |||||||
| Purchase of property, plant and equipment | — | — | 
                                                -1,061,088,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -844,126,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Proceeds from sale of property, plant and equipment | — | — | 
                                                11,555,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                531,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Net cash provided by (used in) investing activities | — | — | 
                                                -962,954,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -754,721,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Other, net | — | — | 
                                                -6,164,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -5,320,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Cash flows from financing activities | |||||||
| Proceeds from issuance of shares | — | — | 
                                                490,400,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Purchase of treasury shares | — | — | 
                                                -490,400,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Dividends paid | — | — | 
                                                -675,217,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -528,783,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Repayments of long-term borrowings | — | — | 
                                                -229,664,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -271,164,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Net cash provided by (used in) financing activities | — | — | 
                                                -911,048,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -806,059,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Repayments of lease liabilities | — | — | 
                                                -6,167,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -6,111,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Effect of exchange rate change on cash and cash equivalents | — | — | 
                                                -11,940,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,685,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Net increase (decrease) in cash and cash equivalents | — | — | 
                                                -487,332,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -381,767,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Cash and cash equivalents | — | 
                                                3,361,588,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                3,848,921,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,230,689,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             |