The KOSPI fell for a fourth consecutive session on the 15th, closing at 6,600, down 66.25 points, or 1.0%, as surging U.S. Treasury yields and Middle East-related oil supply concerns pressured South Korean stocks. The index briefly slipped below 6,600 after opening 0.38% lower at 6,659.25 and briefly recovering above 6,700 in morning trading. Foreign and institutional selling accelerated in the afternoon, with net foreign sales of 1.5 trillion won and institutional sales of about 900 billion won. Retail investors bought more than 800 billion won, but could not offset the selling. Semiconductor leaders limited the decline after much of the market’s concern over slowing AI investment had already been reflected in prices, although semiconductor materials, components and equipment stocks fell more sharply. The KOSDAQ diverged, closing slightly higher after rising more than 2% in the morning. The won weakened beyond 1,350 per dollar as global markets reacted to a rise in the U.S. 10-year Treasury yield to 5%, oil prices reaching $102.33 a barrel, and renewed expectations of a rate increase ahead of this week’s Federal Open Market Committee meeting. Investors are watching the FOMC outcome, developments in the Middle East and the debate over AI infrastructure spending, with market participants warning that volatility could return before the close.