v3.26.1
Fair value measurement - Private warrant liabilities (Details) - Level 3 - JPY (¥)
¥ in Millions
4 Months Ended 12 Months Ended
Mar. 31, 2025
Mar. 31, 2026
Disclosure of fair value measurement of liabilities [line items]    
Financial liabilities at beginning of period ¥ 56 ¥ 12
Change in fair value (45) (9)
Foreign exchange impact 0 1
Financial liabilities at end of period ¥ 12 ¥ 4