Semi-Annual Consolidated Balance Sheet
| Concept | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Semi-annual consolidated balance sheet | |||||||||||||||||||||
| Balance sheet | |||||||||||||||||||||
| Assets | |||||||||||||||||||||
| Current assets | |||||||||||||||||||||
| Cash and deposits | — | — | — | — | 
                                                859,557,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                937,529,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Other | — | — | — | — | 
                                                19,520,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                8,302,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Current assets | — | — | — | — | 
                                                1,142,272,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                1,152,269,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Non-current assets | |||||||||||||||||||||
| Property, plant and equipment | — | — | — | — | 
                                                26,620,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                22,206,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Property, plant and equipment | |||||||||||||||||||||
| Construction in progress | — | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                1,361,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Accumulated depreciation | — | — | — | — | 
                                                -85,727,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                -74,539,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Intangible assets | |||||||||||||||||||||
| Other | — | — | — | — | 
                                                1,954,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                343,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Intangible assets | — | — | — | — | 
                                                118,700,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                83,558,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Investments and other assets | — | — | — | — | 
                                                75,046,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                102,652,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Investments and other assets | |||||||||||||||||||||
| Investment securities | — | — | — | — | 
                                                7,485,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                33,820,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Deferred tax assets | — | — | — | — | 
                                                27,257,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                29,382,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Other | — | — | — | — | 
                                                15,304,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                14,449,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Non-current assets | — | — | — | — | 
                                                220,368,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                208,418,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Deferred assets | — | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                1,885,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Deferred assets | |||||||||||||||||||||
| Share issuance costs | — | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                1,885,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Assets | — | — | — | — | 
                                                1,362,640,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                1,362,572,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Liabilities | |||||||||||||||||||||
| Current liabilities | |||||||||||||||||||||
| Income taxes payable | — | — | — | — | 
                                                13,989,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                7,085,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Other | — | — | — | — | 
                                                34,731,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                27,184,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Current liabilities | — | — | — | — | 
                                                278,021,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                305,320,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Non-current liabilities | |||||||||||||||||||||
| Long-term borrowings | — | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                5,480,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Asset retirement obligations | — | — | — | — | 
                                                3,820,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                3,784,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Non-current liabilities | — | — | — | — | 
                                                3,820,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                9,264,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Liabilities | — | — | — | — | 
                                                281,841,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                314,585,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Provision for bonuses | — | — | — | — | 
                                                22,702,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                17,708,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Net assets | |||||||||||||||||||||
| Shareholders' equity | |||||||||||||||||||||
| Share capital | — | — | — | — | 
                                                1,370,469,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                1,360,679,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Capital surplus | — | — | — | — | 
                                                209,959,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                200,169,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Retained earnings | — | — | — | — | 
                                                -499,629,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                -512,860,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Shareholders' equity | — | — | — | — | 
                                                1,080,798,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                1,047,987,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Net assets | 
                                                1,080,798,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -499,629,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -499,629,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,370,469,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,080,798,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                209,959,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                209,959,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,047,987,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                200,169,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                200,169,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -512,860,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,360,679,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,047,987,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -512,860,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,351,881,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -572,861,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                970,391,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                191,371,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                191,371,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                970,391,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -572,861,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Liabilities and net assets | — | — | — | — | 
                                                1,362,640,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                1,362,572,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — |