Consolidated Balance Sheet
| Concept | As at 2024-09-30 | As at 2024-03-31 | 
|---|---|---|
| Consolidated balance sheet | ||
| Balance sheet | ||
| Assets | ||
| Non-current assets | ||
| Property, plant and equipment | ||
| Buildings, net | 
                                                796,076,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                814,937,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Own-used assets | ||
| Land | 
                                                1,710,972,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,710,972,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Leased assets | — | — | 
| Leased assets, net | 
                                                10,200,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                8,252,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Construction in progress | 
                                                18,718,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                18,826,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Property, plant and equipment | 
                                                3,947,485,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,055,847,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Vehicles | — | — | 
| Vehicles, net | 
                                                3,352,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,024,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Intangible assets | 
                                                209,875,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                210,552,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Software | 
                                                199,159,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                199,836,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Other | 
                                                10,716,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                10,716,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Intangible assets | ||
| Other intangible assets | ||
| Investments and other assets | ||
| Investment securities | 
                                                82,635,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                80,810,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Long-term loans receivable | 
                                                634,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                923,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Investments in capital | 
                                                605,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                605,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Deferred tax assets | 
                                                323,593,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                324,238,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Other | 
                                                143,725,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                146,067,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Distressed receivables | 
                                                83,689,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                84,333,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Allowance for doubtful accounts | 
                                                -83,689,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -84,333,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Investments and other assets | 
                                                995,040,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                991,589,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Long-term prepaid expenses | 
                                                213,224,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                208,321,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Non-current assets | 
                                                5,152,400,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,257,989,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Current assets | ||
| Cash and deposits | 
                                                7,224,966,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,966,433,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Notes receivable - trade | 
                                                40,207,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                52,612,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Contract assets | 
                                                499,776,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,046,791,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Costs on construction contracts in progress | 
                                                3,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                381,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Work in process | 
                                                13,252,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                11,002,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Prepaid expenses | 
                                                649,427,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                440,160,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Raw materials and supplies | 
                                                90,895,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                68,612,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Inventories | 
                                                114,058,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                90,819,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Other | 
                                                48,448,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                50,333,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Advance payments to suppliers | 
                                                115,677,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                54,035,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Allowance for doubtful accounts | 
                                                -5,535,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -12,076,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Current assets | 
                                                8,688,426,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                8,692,111,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Assets | 
                                                13,840,827,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                13,950,101,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Liabilities | ||
| Current liabilities | ||
| Deposits received | 
                                                23,346,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                24,596,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Accounts payable - other | 
                                                116,828,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                192,066,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Income taxes payable | 
                                                184,107,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                180,677,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Lease liabilities | 
                                                4,759,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,006,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Accrued expenses | 
                                                250,776,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                263,856,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Provisions | ||
| Provision for bonuses | 
                                                192,247,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                172,483,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Asset retirement obligations | 
                                                1,111,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,111,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Advances received | 
                                                2,999,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,999,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Current liabilities | 
                                                6,038,598,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,301,025,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Non-current liabilities | ||
| Lease liabilities | 
                                                7,480,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,090,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Provision for retirement benefits for directors (and other officers) | 
                                                71,960,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                80,260,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Other | 
                                                13,178,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                13,178,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Non-current liabilities | 
                                                238,572,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                229,299,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Asset retirement obligations | 
                                                16,083,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                16,083,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Liabilities | 
                                                6,277,171,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,530,324,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Liabilities and net assets | ||
| Shareholders' equity | 
                                                7,525,816,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                7,382,904,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Share capital | 
                                                923,761,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                923,761,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Capital surplus | 
                                                770,533,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                770,533,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Retained earnings | 
                                                5,831,657,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,688,745,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Treasury shares | 
                                                -135,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -135,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Valuation and translation adjustments | 
                                                37,840,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                36,871,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Valuation difference on available-for-sale securities | 
                                                37,840,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                36,871,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets | 
                                                7,563,656,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                7,419,776,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Liabilities and net assets | 
                                                13,840,827,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                13,950,101,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets | ||
| Shareholders' equity | ||
| Valuation and translation adjustments |