v3.26.1
Share-based payments - Narrative (Details)
$ / shares in Units, ¥ in Millions, $ in Millions
12 Months Ended
Mar. 31, 2026
JPY (¥)
Mar. 31, 2026
USD ($)
$ / shares
shares
Mar. 31, 2025
JPY (¥)
Mar. 31, 2024
JPY (¥)
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]        
Share-based compensation ¥ 1,320   ¥ 0 ¥ 0
Restricted share units        
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]        
Share-based compensation ¥ 1,320      
Unrecognized costs of unvested RSUs | $   $ 14    
Weighted-average recognition period 1 year 10 months 17 days      
Service-Based Conditions, Restricted Share Units | Bottom of range        
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]        
Vesting period 10 months      
Service-Based Conditions, Restricted Share Units | Top of range        
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]        
Vesting period 3 years      
Market Conditions, Restricted Share Units        
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]        
Calendar days 30 days      
Market Conditions, Restricted Share Units | Bottom of range        
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]        
Average closing price (in USD per share) | $ / shares   $ 12.00    
Thunder Bridge        
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]        
Ordinary share per unit delivered once vested | shares   1