The benchmark KOSPI closed slightly higher Thursday, following a choppy session in which the main index plunged nearly 2 percent during afternoon trading. The KOSPI opened 1.33 percent higher at 6,650.33 and initially extended its gains before reversing sharply around 2 p.m. It fell to the 6,400 range before rebounding to close at 6,579.48, up 16.76 points, or 0.26 percent, from the previous session. Retail investors led net selling with 955 billion won ($703 million), while foreign investors and institutions sold a net 423.4 billion won and 215.2 billion won, respectively. Corporations were the only major investor group to post net buying, purchasing nearly 1.6 trillion won and helping cushion the selling pressure from the other three groups. Ongoing share buybacks by Samsung Electronics and SK hynix have recently emerged as a buffer against the sell-off. Market bellwethers closed lower. Samsung Electronics closed at 250,000 won, down 0.2 percent from the previous session, while SK hynix fell 1.05 percent to 1.596 million won. The KOSPI's initial gains followed an overnight rebound on Wa