Consolidated Statement Of Cash Flows
| Concept | 2023-01-01 to 2023-12-31 | As at 2023-12-31 | 2022-01-01 to 2022-12-31 | As at 2022-12-31 | As at 2021-12-31 | 
|---|---|---|---|---|---|
| Consolidated statement of cash flows | |||||
| Statement of cash flows | |||||
| Cash flows from operating activities | |||||
| Profit (loss) before income taxes | 
                                                114,118,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                238,487,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Depreciation | 
                                                10,862,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                13,308,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Increase (decrease) in allowance for doubtful accounts | 
                                                -831,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -62,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Increase (decrease) in provision for retirement benefits | 
                                                16,079,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                13,933,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Interest and dividend income | 
                                                -1,710,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -1,203,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Interest expenses | 
                                                28,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                155,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Subtotal | 
                                                381,860,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                29,799,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Decrease (increase) in trade receivables | 
                                                210,084,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                98,520,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Income taxes paid | 
                                                -39,172,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -149,873,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Net cash provided by (used in) operating activities | 
                                                344,370,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -118,912,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Increase (decrease) in trade payables | 
                                                -68,340,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -264,051,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Interest and dividends received | 
                                                1,710,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,203,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Interest paid | 
                                                -28,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -40,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Cash flows from investing activities | |||||
| Purchase of property, plant and equipment | 
                                                -839,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -12,674,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Net cash provided by (used in) investing activities | 
                                                -17,623,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -33,307,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Cash flows from financing activities | |||||
| Proceeds from issuance of shares | 
                                                6,109,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                12,370,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Purchase of treasury shares | 
                                                -17,566,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -55,559,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Dividends paid | 
                                                -122,568,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -103,344,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Net cash provided by (used in) financing activities | 
                                                -116,933,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -212,338,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Repayments of lease liabilities | 
                                                -667,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -655,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Other, net | 
                                                17,760,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -65,148,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Net increase (decrease) in cash and cash equivalents | 
                                                209,813,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -364,557,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Cash and cash equivalents | — | 
                                                1,416,013,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,206,199,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,570,757,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             |