v3.26.1
Lease - Schedule of Book Value of Right-of-use Assets (Details) - JPY (¥)
¥ in Millions
 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
Disclosure of quantitative information about right-of-use assets [line items]      
Balance at beginning ¥ 14,799 ¥ 8,852  
Increase due to new lease agreements and remeasurement of lease liabilities 577 9,069  
Decrease due to termination of lease agreements and remeasurement of lease liabilities (104) (207)  
Depreciation (3,128) (2,822)  
Other 31 (93)  
Balance at end 12,175 14,799 ¥ 8,852
Buildings      
Disclosure of quantitative information about right-of-use assets [line items]      
Balance at beginning 14,466 8,440  
Increase due to new lease agreements and remeasurement of lease liabilities 577 9,026  
Decrease due to termination of lease agreements and remeasurement of lease liabilities (104) (207)  
Depreciation (3,045) (2,732) (2,541)
Other 31 (61)  
Balance at end 11,925 14,466 8,440
Other      
Disclosure of quantitative information about right-of-use assets [line items]      
Balance at beginning 333 412  
Increase due to new lease agreements and remeasurement of lease liabilities 0 43  
Decrease due to termination of lease agreements and remeasurement of lease liabilities 0 0  
Depreciation (83) (90) (64)
Other 0 (32)  
Balance at end ¥ 250 ¥ 333 ¥ 412