Treasury Shares, Etc.
| Concept | 
                                    
                                        As at 2022-12-31  | 
                            
                                
                                    
                                        As at 2022-12-31  | 
                            
                        
|---|---|---|
| Treasury shares, etc. | ||
| Treasury shares, etc. | ||
| Name of shareholder | 
                                        
                                             
                                                東洋炭素㈱
                                                
                                             
                                        
                                     | 
                                
                                    — | 
| Address of shareholder | 
                                        
                                             
                                                大阪市西淀川区竹島五丁目7番12号
                                                
                                             
                                        
                                     | 
                                
                                    — | 
| Number of shares held in own name | 
                                        
                                             
                                                20,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                20,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Number of shares held in others' names | 
                                        
                                             
                                                
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Total number of shares held | 
                                        
                                             
                                                20,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                20,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Shareholding ratio | 
                                        
                                             
                                                0.0010
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                0.0010
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             
                                        
                                     |