Quarterly Consolidated Balance Sheet
| Concept | 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 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 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 | 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 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2022-03-31 | As at 2022-03-31 | As at 2022-03-31 | As at 2022-03-31 | As at 2022-03-31 | As at 2022-03-31 | As at 2022-03-31 | As at 2022-03-31 | As at 2022-03-31 | As at 2022-03-31 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Quarterly consolidated balance sheet | ||||||||||||||||||||||||||||||||||||||||||||||
| Balance sheet | ||||||||||||||||||||||||||||||||||||||||||||||
| Assets | ||||||||||||||||||||||||||||||||||||||||||||||
| Current assets | ||||||||||||||||||||||||||||||||||||||||||||||
| Cash and deposits | — | — | — | — | — | — | — | — | — | — | 
                                                5,561,008,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                5,499,108,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                2,941,896,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Securities | — | — | — | — | — | — | — | — | — | — | 
                                                21,262,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                21,262,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Work in process | — | — | — | — | — | — | — | — | — | — | 
                                                1,033,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Raw materials and supplies | — | — | — | — | — | — | — | — | — | — | 
                                                10,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Inventories | — | — | — | — | — | — | — | — | — | — | 
                                                1,043,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,043,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                4,738,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Other | — | — | — | — | — | — | — | — | — | — | 
                                                28,768,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                15,771,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                7,442,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Current assets | — | — | — | — | — | — | — | — | — | — | 
                                                5,612,137,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                5,552,109,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                2,977,402,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Non-current assets | ||||||||||||||||||||||||||||||||||||||||||||||
| Property, plant and equipment | — | — | — | — | — | — | — | — | — | — | 
                                                514,104,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                514,104,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                562,147,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Property, plant and equipment | ||||||||||||||||||||||||||||||||||||||||||||||
| Buildings and structures | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Buildings and structures, net | — | — | — | — | — | — | — | — | — | — | 
                                                391,593,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Machinery, equipment and vehicles | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Machinery, equipment and vehicles, net | — | — | — | — | — | — | — | — | — | — | 
                                                85,409,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Other | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Other, net | — | — | — | — | — | — | — | — | — | — | 
                                                37,101,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Accumulated depreciation | — | — | — | — | — | — | — | — | — | — | 
                                                -372,647,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Intangible assets | ||||||||||||||||||||||||||||||||||||||||||||||
| Other | — | — | — | — | — | — | — | — | — | — | 
                                                17,079,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                15,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                5,500,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Intangible assets | — | — | — | — | — | — | — | — | — | — | 
                                                17,079,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                17,079,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                5,500,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Investments and other assets | — | — | — | — | — | — | — | — | — | — | 
                                                41,417,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                101,417,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                42,368,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Investments and other assets | ||||||||||||||||||||||||||||||||||||||||||||||
| Other | — | — | — | — | — | — | — | — | — | — | 
                                                41,417,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                41,417,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                42,368,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Non-current assets | — | — | — | — | — | — | — | — | — | — | 
                                                572,600,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                632,600,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                610,015,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Assets | — | — | — | — | — | — | — | — | — | — | 
                                                6,184,738,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                6,184,710,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                3,587,417,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Liabilities | ||||||||||||||||||||||||||||||||||||||||||||||
| Current liabilities | ||||||||||||||||||||||||||||||||||||||||||||||
| Income taxes payable | — | — | — | — | — | — | — | — | — | — | 
                                                46,097,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                46,052,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                2,850,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Current liabilities | — | — | — | — | — | — | — | — | — | — | 
                                                166,015,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                165,970,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                97,425,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Non-current liabilities | ||||||||||||||||||||||||||||||||||||||||||||||
| Asset retirement obligations | — | — | — | — | — | — | — | — | — | — | 
                                                28,437,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                28,437,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                28,365,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Non-current liabilities | — | — | — | — | — | — | — | — | — | — | 
                                                34,945,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                34,945,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                36,369,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Liabilities | — | — | — | — | — | — | — | — | — | — | 
                                                200,960,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                200,915,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                133,794,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Net assets | ||||||||||||||||||||||||||||||||||||||||||||||
| Shareholders' equity | ||||||||||||||||||||||||||||||||||||||||||||||
| Share capital | — | — | — | — | — | — | — | — | — | — | 
                                                1,594,960,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,594,960,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                10,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Capital surplus | — | — | — | — | — | — | — | — | — | — | 
                                                6,493,705,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                6,493,705,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                4,908,744,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Retained earnings | — | — | — | — | — | — | — | — | — | — | 
                                                -2,102,138,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -2,100,222,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                -1,469,955,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Treasury shares | — | — | — | — | — | — | — | — | — | — | 
                                                -12,016,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -12,016,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                -11,748,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Shareholders' equity | — | — | — | — | — | — | — | — | — | — | 
                                                5,974,510,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                5,976,427,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                3,437,041,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Share acquisition rights | — | — | — | — | — | — | — | — | — | — | 
                                                7,766,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                7,366,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                16,582,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Non-controlling interests | — | — | — | — | — | — | — | — | — | — | 
                                                1,500,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Net assets | 
                                                5,976,427,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,040,211,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,493,705,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -12,016,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -2,100,222,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                7,366,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -12,016,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,453,493,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,493,705,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,594,960,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,983,777,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,974,510,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                7,766,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,983,794,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,500,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,594,960,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -2,102,138,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -2,100,222,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                10,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                10,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -1,469,955,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,453,493,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,437,041,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,453,623,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,908,744,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,908,744,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -11,748,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,453,623,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                16,582,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,455,250,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -11,748,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,437,041,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -1,469,955,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -1,469,955,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                16,582,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,455,250,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -16,764,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -1,017,877,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,449,145,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                10,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                15,792,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,895,546,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -1,017,877,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,904,396,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,879,754,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Liabilities and net assets | — | — | — | — | — | — | — | — | — | — | 
                                                6,184,738,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                6,184,710,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                3,587,417,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |