Consolidated Balance Sheet
| Concept | As at 2023-12-31 | As at 2023-03-31 | 
|---|---|---|
| Consolidated balance sheet | ||
| Balance sheet | ||
| Assets | ||
| Current assets | ||
| Cash and deposits | 
                                                3,583,326,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,419,047,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Accounts receivable - trade | 
                                                707,249,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                748,063,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Work in process | 
                                                1,059,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,464,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Prepaid expenses | 
                                                51,690,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                54,696,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Supplies | 
                                                1,112,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,247,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Other | 
                                                15,148,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                8,058,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Current assets | 
                                                4,359,586,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,233,577,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Non-current assets | ||
| Property, plant and equipment | 
                                                1,228,806,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,241,696,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Buildings, net | 
                                                257,513,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                266,030,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Land | 
                                                968,059,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                968,059,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Leased assets, net | 
                                                867,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,647,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Property, plant and equipment | ||
| Own-used assets | ||
| Leased assets | 
                                                5,202,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,202,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Accumulated depreciation | 
                                                -4,335,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -3,554,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Vehicles | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,865,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Accumulated depreciation | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -2,921,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Vehicles, net | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,943,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Intangible assets | ||
| Other | 
                                                1,506,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,510,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Other intangible assets | ||
| Intangible assets | 
                                                14,595,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                19,292,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Software | 
                                                13,088,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                17,782,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Investments and other assets | 
                                                335,432,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                273,473,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Investment securities | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,078,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Long-term prepaid expenses | 
                                                77,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                143,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Deferred tax assets | 
                                                309,288,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                243,868,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Allowance for doubtful accounts | 
                                                -1,800,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -1,800,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Other | 
                                                27,867,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                27,183,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Investments and other assets | ||
| Non-current assets | 
                                                1,578,834,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,534,462,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Assets | 
                                                5,938,420,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,768,040,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Liabilities and net assets | ||
| Non-current liabilities | 
                                                694,576,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                632,467,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Lease liabilities | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                667,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Current liabilities | 
                                                1,432,016,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,500,581,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Short-term borrowings | 
                                                600,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                600,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Accounts payable - other | 
                                                55,641,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                21,069,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Accrued expenses | 
                                                386,656,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                362,426,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Deposits received | 
                                                93,937,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                21,392,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Liabilities | 
                                                2,126,592,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,133,049,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Shareholders' equity | 
                                                3,811,828,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,634,991,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Share capital | 
                                                377,525,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                377,525,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Capital surplus | 
                                                337,525,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                337,525,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Retained earnings | 
                                                3,096,860,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,920,023,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Treasury shares | 
                                                -81,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -81,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets | 
                                                3,811,828,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,634,991,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Liabilities and net assets | 
                                                5,938,420,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,768,040,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Liabilities | ||
| Current liabilities | ||
| Income taxes payable | 
                                                34,881,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                106,800,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Lease liabilities | 
                                                953,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,144,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Provisions | ||
| Provision for bonuses | 
                                                157,767,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                278,538,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Other | 
                                                102,178,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                109,210,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Non-current liabilities | ||
| Provision for retirement benefits for directors (and other officers) | 
                                                243,352,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                179,118,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets | ||
| Shareholders' equity |