South Korean retail investors bought a net 2.21 trillion won ($1.6 billion) of KOSPI shares on Sept. 28, taking the opposite side of heavy foreign and institutional selling during a 2.70% market decline. The KOSPI closed at 6,889.75 after reopening from the Chuseok holiday, with foreign investors selling 3.23 trillion won ($2.4 billion) and institutions selling 1.02 trillion won ($750 million). Individuals increased purchases from about 145 billion won early in the session, viewing the decline as a buying opportunity. Foreign investors cited dollar strength and short-term concerns over South Korea's semiconductor sector, while institutions including financial investment firms, investment trusts and pension funds also sold. Samsung Electronics and SK hynix each fell more than 5%, extending volatility in the KOSPI. The two chipmakers will be closely watched for evidence of whether retail demand establishes support or whether foreign selling continues. The KOSDAQ, South Korea's secondary market, ended modestly higher.