Balance Sheet
| Concept | As at 2024-03-31 | As at 2023-12-31 | 
|---|---|---|
| Balance sheet | ||
| Balance sheet | ||
| Assets | ||
| Current assets | ||
| Cash and deposits | 
                                                2,934,171,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,266,408,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Prepaid expenses | 
                                                15,603,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                31,374,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Raw materials and supplies | 
                                                9,364,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                10,794,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Other | 
                                                7,982,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                391,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Current assets | 
                                                2,967,122,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,308,968,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Non-current assets | ||
| Investments and other assets | 
                                                4,934,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,934,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Investments and other assets | ||
| Non-current assets | 
                                                4,934,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,934,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Other assets | ||
| Assets | 
                                                2,972,056,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,313,902,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Other assets | — | — | 
| Other assets | — | — | 
| Liabilities | ||
| Non-current liabilities | ||
| Non-current liabilities | 
                                                31,297,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                30,654,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Asset retirement obligations | 
                                                31,297,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                30,654,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Current liabilities | 
                                                69,439,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                178,480,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Accounts payable - trade | 
                                                6,523,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                11,794,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Accounts payable - other | 
                                                1,121,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                7,271,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Accrued expenses | 
                                                59,513,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                30,116,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Income taxes payable | 
                                                577,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                69,583,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Deposits received | 
                                                1,703,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Other | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                59,714,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Current liabilities | ||
| Deposits received | ||
| Liabilities | 
                                                100,736,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                209,134,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Other liabilities | — | — | 
| Other liabilities | — | — | 
| Liabilities and net assets | ||
| Shareholders' equity | 
                                                2,871,319,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,104,768,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Share capital | 
                                                854,087,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                854,087,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Capital surplus | 
                                                3,003,337,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,003,337,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Retained earnings | 
                                                -986,104,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -752,656,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets | 
                                                2,871,319,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,104,768,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Liabilities and net assets | 
                                                2,972,056,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,313,902,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets | ||
| Shareholders' equity | ||
| Capital surplus | ||
| Retained earnings |