The Nikkei 225 Index dropped 12.4% to close at 31,458, and the Topix Index fell 12.23% to 2,227 on Monday, both hitting nine-month lows. This marked the worst one-day decline for Japanese shares since "Black Monday" in 1987, pushing them into bear market territory. The sell-off was driven by concerns over potential interest rate hikes in Japan, following the Bank of Japan's recent policy rate increase to 0.25% and indications of further hikes expected before March 2025.