The Nikkei 225's largest one-day percentage fall during the 1987 crash was 14.9%.
Japan's market was among the major exchanges affected by the international selling wave on October 20, 1987, the day after Black Monday in New York. The Nikkei 225 fell 3,836.48 points, or 14.9%, in one session.
The decline reflected the global nature of the crash. Financial markets were increasingly connected through international investors, currency markets, and rapidly transmitted information. A sharp fall in one major center could therefore influence trading decisions elsewhere almost immediately.
This record concerns the Nikkei 225's percentage decline during the 1987 crash, not its later points-based records. Japan subsequently experienced a separate and much longer market collapse after its late-1980s asset-price bubble burst.