Consolidated Statement Of Income
| Concept | 
                                    
                                        2024-01-01 to 2024-03-31  | 
                            
                                
                                    
                                        2024-01-01 to 2024-03-31  | 
                            
                                
                                    
                                        2024-01-01 to 2024-03-31  | 
                            
                                
                                    
                                        2024-01-01 to 2024-03-31  | 
                            
                                
                                    
                                        2024-01-01 to 2024-03-31  | 
                            
                                
                                    
                                        2023-01-01 to 2023-03-31  | 
                            
                                
                                    
                                        2023-01-01 to 2023-03-31  | 
                            
                                
                                    
                                        2023-01-01 to 2023-03-31  | 
                            
                                
                                    
                                        2023-01-01 to 2023-03-31  | 
                            
                                
                                    
                                        2023-01-01 to 2023-03-31  | 
                            
                        
|---|---|---|---|---|---|---|---|---|---|---|
| Consolidated statement of income | ||||||||||
| Statement of income | ||||||||||
| Net sales | 
                                        
                                             
                                                2,218,311,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                804,373,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                2,218,311,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                1,413,938,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                2,052,431,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                1,283,751,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                768,680,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                2,052,431,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Operating expenses | ||||||||||
| Selling, general and administrative expenses | — | — | — | 
                                        
                                             
                                                604,342,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | 
                                        
                                             
                                                515,802,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Cost of sales | — | — | — | 
                                        
                                             
                                                946,624,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | 
                                        
                                             
                                                916,750,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Operating expenses | ||||||||||
| Operating profit (loss) | 
                                        
                                             
                                                717,952,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                -50,607,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                36,319,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                667,344,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                681,632,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                652,083,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                -32,205,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                651,449,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                634,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                619,878,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Ordinary profit (loss) | — | — | — | 
                                        
                                             
                                                671,209,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | 
                                        
                                             
                                                622,950,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Gross profit (loss) | — | — | — | 
                                        
                                             
                                                1,271,686,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | 
                                        
                                             
                                                1,135,680,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Net sales | ||||||||||
| Non-operating income | ||||||||||
| Non-operating income | — | — | — | 
                                        
                                             
                                                3,868,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | 
                                        
                                             
                                                3,074,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Miscellaneous income | — | — | — | 
                                        
                                             
                                                1,911,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | 
                                        
                                             
                                                971,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Cost of sales | ||||||||||
| Selling, general and administrative expenses | ||||||||||
| Non-operating expenses | ||||||||||
| Non-operating expenses | — | — | — | 
                                        
                                             
                                                3,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | 
                                        
                                             
                                                1,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Gross profit | ||||||||||
| Profit (loss) before income taxes | — | — | — | 
                                        
                                             
                                                671,209,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | 
                                        
                                             
                                                622,950,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Income taxes - current | — | — | — | 
                                        
                                             
                                                237,380,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | 
                                        
                                             
                                                139,935,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Income taxes - deferred | — | — | — | 
                                        
                                             
                                                -48,942,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | 
                                        
                                             
                                                -34,035,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Income taxes | — | — | — | 
                                        
                                             
                                                188,437,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | 
                                        
                                             
                                                105,899,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Profit (loss) | — | — | — | 
                                        
                                             
                                                482,772,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | 
                                        
                                             
                                                517,051,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     |