The KOSPI opened lower on the 10th as quadruple witching (simultaneous expiry of four derivatives types) heightened uncertainty over supply and demand. The index was down 16.65 points, or 0.24%, at 7,034.99 as of 9:12 a.m., after briefly moving into positive territory. Institutional investors were net sellers of 166.1 billion won, while foreign and retail investors bought 45.5 billion won and 28.7 billion won, respectively. The decline followed a third consecutive drop in New York stocks, where higher oil prices and U.S. Treasury yields pressured risk appetite. Analysts said foreign futures flows and program trading could amplify KOSPI volatility during the session. Kiwoom Securities analyst Han Ji-young said the index could surrender part of the previous day's gains, although Samsung Electronics and SK hynix buybacks and foreign investors' net buying in September were supporting downside resilience.