Consolidated Balance Sheet
| Concept | As at 2024-03-31 | As at 2023-09-30 | 
|---|---|---|
| Consolidated balance sheet | ||
| Balance sheet | ||
| Assets | ||
| Non-current assets | 
                                                13,134,415,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                13,835,333,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Investments and other assets | 
                                                6,109,403,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                7,010,981,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Investment securities | 
                                                2,482,412,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,274,380,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Long-term loans receivable | 
                                                10,670,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Deferred tax assets | 
                                                216,175,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                532,115,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Other | 
                                                2,744,123,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,561,944,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Allowance for doubtful accounts | 
                                                -109,158,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -116,337,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Current assets | ||
| Cash and deposits | 
                                                10,212,251,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                10,246,176,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Notes receivable, accounts receivable from completed construction contracts and other | 
                                                16,329,390,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                14,383,189,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Costs on construction contracts in progress | 
                                                2,931,296,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,960,167,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Other | 
                                                1,007,363,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,087,487,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Allowance for doubtful accounts | 
                                                -18,517,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -17,003,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Current assets | 
                                                32,121,287,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                30,167,212,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Non-current assets | ||
| Property, plant and equipment | 
                                                6,575,994,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,606,533,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Land | 
                                                5,130,060,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,145,860,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Leased assets, net | 
                                                48,905,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                43,821,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Construction in progress | 
                                                498,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,957,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Property, plant and equipment | ||
| Buildings and structures | — | — | 
| Buildings and structures, net | 
                                                1,291,906,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,313,291,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Own-used assets | ||
| Machinery, equipment and vehicles | — | — | 
| Machinery, equipment and vehicles, net | 
                                                8,134,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,689,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Leased assets | — | — | 
| Intangible assets | ||
| Goodwill | 
                                                314,040,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                90,702,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Other | 
                                                134,977,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                127,115,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Other intangible assets | ||
| Intangible assets | 
                                                449,017,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                217,818,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Investments and other assets | ||
| Retirement benefit asset | 
                                                765,181,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                753,878,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Assets | 
                                                45,255,702,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                44,002,545,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Liabilities | ||
| Current liabilities | ||
| Notes payable, accounts payable for construction contracts and other | 
                                                9,871,246,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                9,100,863,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Short-term borrowings | 
                                                1,000,247,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                290,938,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Income taxes payable | 
                                                305,352,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                429,949,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Lease liabilities | 
                                                20,122,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                18,124,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Advances received on construction contracts in progress | 
                                                912,194,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,203,625,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Other | 
                                                1,928,887,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,773,082,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Current liabilities | 
                                                18,708,627,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                18,271,131,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Non-current liabilities | ||
| Long-term borrowings | 
                                                123,750,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                171,850,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Deferred tax liabilities | 
                                                99,392,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                83,072,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Retirement benefit liability | 
                                                124,822,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                100,035,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Lease liabilities | 
                                                33,283,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                30,079,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Other | 
                                                803,768,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                809,065,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Non-current liabilities | 
                                                1,546,032,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,551,896,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Liabilities | 
                                                20,254,660,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                19,823,027,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Liabilities and net assets | ||
| Shareholders' equity | 
                                                24,257,129,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                23,538,316,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Share capital | 
                                                896,350,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                896,350,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Capital surplus | 
                                                1,360,916,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,360,916,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Retained earnings | 
                                                22,033,516,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                21,314,702,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Treasury shares | 
                                                -33,652,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -33,652,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Valuation and translation adjustments | 
                                                743,911,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                641,201,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Valuation difference on available-for-sale securities | 
                                                430,391,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                304,945,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets | 
                                                25,001,041,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                24,179,517,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Liabilities and net assets | 
                                                45,255,702,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                44,002,545,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets | ||
| Shareholders' equity | ||
| Valuation and translation adjustments | ||
| Remeasurements of defined benefit plans | 
                                                313,520,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                336,255,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             |