Semi-Annual Balance Sheet
| Concept | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2022-03-31 | As at 2022-03-31 | As at 2022-03-31 | As at 2022-03-31 | As at 2022-03-31 | As at 2022-03-31 | As at 2022-03-31 | As at 2022-03-31 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Semi-annual balance sheet | ||||||||||||||||||||||||
| Balance sheet | ||||||||||||||||||||||||
| Assets | ||||||||||||||||||||||||
| Current assets | ||||||||||||||||||||||||
| Cash and deposits | — | — | — | — | — | — | 
                                                3,038,139,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                2,258,679,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Securities | — | — | — | — | — | — | 
                                                100,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Other | — | — | — | — | — | — | 
                                                6,952,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                8,419,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Current assets | — | — | — | — | — | — | 
                                                5,040,054,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                4,243,724,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Prepaid expenses | — | — | — | — | — | — | 
                                                31,254,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                26,311,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Non-current assets | ||||||||||||||||||||||||
| Property, plant and equipment | — | — | — | — | — | — | 
                                                92,014,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                92,553,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Property, plant and equipment | ||||||||||||||||||||||||
| Buildings | — | — | — | — | — | — | 
                                                92,654,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                92,654,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Accumulated depreciation | — | — | — | — | — | — | 
                                                -43,792,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -39,517,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Buildings, net | — | — | — | — | — | — | 
                                                48,862,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                53,136,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Tools, furniture and fixtures | — | — | — | — | — | — | 
                                                216,928,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                199,545,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Accumulated depreciation | — | — | — | — | — | — | 
                                                -173,775,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -160,128,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Tools, furniture and fixtures, net | — | — | — | — | — | — | 
                                                43,152,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                39,417,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Intangible assets | ||||||||||||||||||||||||
| Intangible assets | — | — | — | — | — | — | 
                                                1,136,408,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,218,977,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Software | — | — | — | — | — | — | 
                                                938,453,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,074,574,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Investments and other assets | ||||||||||||||||||||||||
| Investment securities | — | — | — | — | — | — | 
                                                3,197,677,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                3,297,441,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Investments and other assets | — | — | — | — | — | — | 
                                                3,642,253,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                3,725,838,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Deferred tax assets | — | — | — | — | — | — | 
                                                242,350,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                227,400,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Other | — | — | — | — | — | — | 
                                                1,097,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Non-current assets | — | — | — | — | — | — | 
                                                4,870,677,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                5,037,369,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Assets | — | — | — | — | — | — | 
                                                9,910,732,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                9,281,093,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Liabilities | ||||||||||||||||||||||||
| Current liabilities | ||||||||||||||||||||||||
| Accounts payable - trade | — | — | — | — | — | — | 
                                                289,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                358,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Income taxes payable | — | — | — | — | — | — | 
                                                232,453,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                150,347,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Current liabilities | — | — | — | — | — | — | 
                                                795,414,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                669,408,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Advances received | — | — | — | — | — | — | 
                                                2,433,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                3,730,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Accounts payable - other | — | — | — | — | — | — | 
                                                306,375,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                289,092,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Non-current liabilities | ||||||||||||||||||||||||
| Non-current liabilities | — | — | — | — | — | — | 
                                                597,778,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                587,604,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Asset retirement obligations | — | — | — | — | — | — | 
                                                19,335,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                19,174,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Other | — | — | — | — | — | — | 
                                                7,009,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Liabilities | — | — | — | — | — | — | 
                                                1,393,193,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,257,012,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Other liabilities | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Provision for retirement benefits | — | — | — | — | — | — | 
                                                571,434,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                568,430,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Provision for bonuses | — | — | — | — | — | — | 
                                                143,445,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                119,413,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Other liabilities | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Net assets | ||||||||||||||||||||||||
| Share capital | — | — | — | — | — | — | 
                                                783,200,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                783,200,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Shareholders' equity | ||||||||||||||||||||||||
| Capital surplus | ||||||||||||||||||||||||
| Legal capital surplus | — | — | — | — | — | — | 
                                                1,461,260,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,461,260,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Capital surplus | — | — | — | — | — | — | 
                                                1,461,260,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,461,260,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Retained earnings | ||||||||||||||||||||||||
| Legal retained earnings | — | — | — | — | — | — | 
                                                17,397,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                17,397,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Other retained earnings | ||||||||||||||||||||||||
| Retained earnings brought forward | — | — | — | — | — | — | 
                                                6,255,732,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                5,762,227,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Other retained earnings | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Retained earnings | — | — | — | — | — | — | 
                                                6,273,130,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                5,779,624,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Treasury shares | — | — | — | — | — | — | 
                                                -51,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -3,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Shareholders' equity | — | — | — | — | — | — | 
                                                8,517,538,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                8,024,080,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Net assets | 
                                                8,517,538,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,461,260,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -51,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,273,130,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                783,200,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                17,397,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                8,517,538,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,255,732,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                783,200,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,762,227,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                8,024,080,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,461,260,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -3,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                8,024,080,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,779,624,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                17,397,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,461,260,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -3,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,325,204,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                783,200,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                17,397,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                7,569,660,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,307,807,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                7,569,660,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Liabilities and net assets | — | — | — | — | — | — | 
                                                9,910,732,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                9,281,093,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — |