Related Party Transactions - Summary of Significant Balances and Transactions Between Group and Related Parties Equity Transactions (Details) ¥ in Millions	12 Months Ended
	Mar. 31, 2026 JPY (¥)
Parent Company \| SoftBank Corp. \| Acquisition of Shares
Disclosure of transactions between related parties [line items]
Equity transactions	¥ 5,727
Parent Company \| SoftBank Corp. \| Issuance of New Shares
Disclosure of transactions between related parties [line items]
Equity transactions	34,889
Parent Company \| LY Corporation \| Acquisition of Shares
Disclosure of transactions between related parties [line items]
Equity transactions	80
Parent Company \| LY Corporation \| Issuance of New Shares
Disclosure of transactions between related parties [line items]
Equity transactions	34,889
Other affiliated company \| SVF II Piranha (DE) LLC \| Exercise of Stock Options
Disclosure of transactions between related parties [line items]
Equity transactions	15,901
Other affiliated company \| SVF II Piranha (DE) LLC \| Issuance of New Shares
Disclosure of transactions between related parties [line items]
Equity transactions	35,944
Subsidiary of Parent Company \| Z Financial Corporation \| Acquisition of Shares
Disclosure of transactions between related parties [line items]
Equity transactions	¥ 117,000