v3.26.1
Fair value measurement - Equity security investments (Details) - JPY (¥)
¥ in Millions
12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Changes in fair value measurement, assets [abstract]    
Balance at beginning of period ¥ 62,190  
Balance at end of period 61,931 ¥ 62,190
Level 3    
Changes in fair value measurement, assets [abstract]    
Balance at beginning of period 46 39
Purchases 10 21
Additions (business combination) 14 0
Change in fair value (16) (4)
Foreign exchange impact 0 (10)
Balance at end of period ¥ 54 ¥ 46