The Korea Composite Stock Price Index (KOSPI) plunged 7.57% on October 15, closing at 5554.22 points, after briefly falling to around 5400 points during the session. Both the KOSPI and KOSDAQ markets triggered circuit breakers on the sell side and Level 1 halts on the same day, the first time this has happened in approximately two and a half months. Foreign investors' net selling of KOSPI reached 4.8196 trillion Korean Won (approximately $3.6 billion) in a single day, becoming the primary driver of this sharp decline. The trigger for this downturn was the higher-than-expected US September CPI data, which fueled concerns about Federal Reserve interest rate hikes. Simultaneously, rising doubts about the sustainability of AI investments led to declines in the Nasdaq index and NVIDIA's stock price.