Consolidated Statement Of Cash Flows
| Concept | 2024-01-01 to 2024-06-30 | As at 2024-06-30 | As at 2023-12-31 | As at 2023-06-30 | 2023-01-01 to 2023-06-30 | As at 2022-12-31 | 
|---|---|---|---|---|---|---|
| Consolidated statement of cash flows | ||||||
| Statement of cash flows | ||||||
| Cash flows from operating activities | ||||||
| Subtotal | 
                                                118,558,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                119,465,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Interest and dividends received | 
                                                16,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                8,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Income taxes paid | 
                                                -94,628,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -96,062,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Interest paid | 
                                                -8,980,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -11,579,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) operating activities | 
                                                -4,833,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                11,831,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash flows from investing activities | ||||||
| Purchase of property, plant and equipment | 
                                                -1,196,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -284,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Purchase of investment securities | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -29,900,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) investing activities | 
                                                80,549,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -91,573,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Proceeds from sale of investment securities | 
                                                108,199,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash flows from financing activities | ||||||
| Proceeds from long-term borrowings | 
                                                49,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Repayments of long-term borrowings | 
                                                -210,271,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -172,366,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Proceeds from sale of shares of subsidiaries not resulting in change in scope of consolidation | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                490,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) financing activities | 
                                                -547,386,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                306,405,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Effect of exchange rate change on cash and cash equivalents | 
                                                2,674,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,310,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net increase (decrease) in cash and cash equivalents | 
                                                -468,996,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                227,973,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | — | 
                                                967,027,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,436,023,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,159,894,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                898,182,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             |