v3.25.2
Fair value measurement - Equity security investments (Details) - JPY (¥)
¥ in Millions
12 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Changes in fair value measurement, assets [abstract]    
Balance, beginning of period ¥ 72,280  
Balance, end of period 62,190 ¥ 72,280
Level 3    
Changes in fair value measurement, assets [abstract]    
Balance, beginning of period 39 40
Fair value recorded in connection with acquisition 21 10
Change in fair value (4) (11)
Settlement (10) 0
Balance, end of period ¥ 46 ¥ 39