Kospi Flat on Quadruple Witching Day as Foreign and Institutional Investors Sell

South Korea's Kospi traded little changed near the 7,060 mark in early dealings on Sept. 10 as foreign and institutional investors sold on the so-called quadruple witching day, when stock-index futures and options and single-stock futures and options expire at the same time.

As of 9:02 a.m., the Kospi was up 0.1% from the previous session at 7,058.75. The benchmark swung between gains and losses shortly after the open and showed no clear direction.

Quadruple witching day can amplify intraday volatility as derivatives expiration concentrates program trading and position adjustments by foreign investors.

Retail investors were propping up the market. Individuals were net buyers of 385.7 billion won on the main board, while institutions and foreign investors were net sellers of 374.3 billion won and 11.5 billion won, respectively.

U.S. stocks fell overnight as rising oil prices and Treasury yields weighed on sentiment. Brent crude for November delivery climbed $3.29, or 3.36%, to settle at $101.21 a barrel as tensions in the Middle East flared again.

The settlement was the highest since May 22 and marked the first close above $100 a barrel since July 23.

In the U.S. bond market, yields continued to rise. The 10-year Treasury yield climbed as high as 4.85% intraday, the highest level since November 2023.

Large-cap semiconductor shares advanced. Samsung Electronics rose 0.19% and SK Hynix added 1.19% as expectations for the artificial intelligence industry, led by OpenAI, remained strong.

The Kosdaq underperformed. At the same time, the index was down 1.08% at 821.42 as foreign and institutional investors both sold.

On the Kosdaq, foreign investors were net sellers of 125.5 billion won and institutions sold 35.8 billion won, while retail investors bought a net 167.3 billion won.

By stock, robot-related shares were strong. Yuil Robotics jumped 14.93%, while Robotis and Clobot rose 5.65% and 4.48%, respectively.