Crypto assets held - Changes in Crypto Assets Held (Details) - JPY (¥) ¥ in Millions |
12 Months Ended | |
|---|---|---|
Mar. 31, 2026 |
Mar. 31, 2025 |
|
| Reconciliation Of Changes In Crypto Assets [Abstract] | ||
| Crypto assets held (non-current assets), beginning balance | ¥ 43 | |
| Crypto assets held (non-current assets), ending balance | 186 | ¥ 43 |
| Cryptocurrency | ||
| Reconciliation Of Changes In Crypto Assets [Abstract] | ||
| Crypto assets held (non-current assets), beginning balance | 0 | |
| Additions (by business combination) | 208 | 21 |
| Additions (not by business combination) | 2,230 | 458 |
| Disposals | 2,304 | ¥ 435 |
| Foreign currency translation adjustments | ¥ 10 | |