v3.26.1
Related parties - Related Party Transactions (Details)
$ in Millions
12 Months Ended
Mar. 31, 2026
JPY (¥)
Mar. 31, 2025
JPY (¥)
Mar. 31, 2024
JPY (¥)
Mar. 31, 2026
USD ($)
Sep. 01, 2025
JPY (¥)
Disclosure of transactions between related parties [line items]          
Percentage of entity's revenue 5.00%        
Cash repayments of advances and loans from related parties ¥ 17,758,000,000 ¥ 7,887,000,000 ¥ 0    
Parent company          
Disclosure of transactions between related parties [line items]          
Business management service fee 0 397,000,000 458,000,000    
Total for all subsidiaries          
Disclosure of transactions between related parties [line items]          
Borrowing 2,524,000,000 751,000,000      
Interest Expense, Related Party Transactions 144,000,000 21,000,000 0    
Total for all subsidiaries | Line Of Credit 6,000 Million          
Disclosure of transactions between related parties [line items]          
Borrowing ¥ 0 0      
Borrowings, interest rate 1.75%     1.75%  
Total for all subsidiaries | Line Of Credit 2,400 Million          
Disclosure of transactions between related parties [line items]          
Borrowing ¥ 2,024,000,000 ¥ 751,000,000      
Line or credit, aggregate commitments ¥ 2,554,000,000     $ 16  
Borrowings, interest rate 5.92% 5.69%   5.92%  
Total for all subsidiaries | Line Of Credit 5,000 Million          
Disclosure of transactions between related parties [line items]          
Line or credit, aggregate commitments ¥ 5,000,000,000 ¥ 6,000,000,000     ¥ 500,000,000
Borrowings, interest rate         9.50%
Associates of parent company          
Disclosure of transactions between related parties [line items]          
Provision Of Sales Service, Amounts Payables, Related Party Transactions 3,000,000 5,000,000      
Transaction revenue 8,314,000,000 6,396,000,000 847,000,000    
Cost of sales 8,555,000,000 6,377,000,000 844,000,000    
Provision Of Sales Service, Related Party Transactions ¥ 42,000,000 ¥ 42,000,000 ¥ 26,000,000