[Edaily Reporter KIM YOON-JEONG ] The KOSPI jumped more than 2% in early trading on the 22nd, breaking through the 7,100 mark, but closed around 7,010 after giving up most of its gains. Buoyed by the rally in U.S. artificial intelligence (AI) stocks overnight, SamsungElectronics and SK hynix rose by around 3% in early trading, lifting the index, but momentum faded in the afternoon. In particular, foreign and institutional investors bought SamsungElectronics while selling SK hynix; as a result, SamsungElectronics rose by less than 1%, while SK hynix turned negative, showing divergent trends among the two leading semiconductor stocks.

◇Rising on AI, Pressured by Oil Prices… KOSPI Briefly Drops Below 7,000 During the Session
According to the Korea Exchange, the KOSPI closed at 7,017.91 on that day, up 10.19 points (0.15%) from the previous trading day. The index opened at 7,161.61, up 153.89 points (2.20%) from the previous close, and rose as high as 7,171.44 during the session but quickly pared its gains. At one point in the afternoon, it dipped to 6,986.27, briefly falling below the 7,000 mark.
On the stock market that day, retail investors and institutional investors were net sellers of 1.6065 trillion won and 123.6 billion won, respectively. In contrast, other corporate entities were net buyers of 1.6525 trillion won, and foreign investors were net buyers of 86.3 billion won.
The early-session rally in the stock market is believed to have been driven by the positive momentum from the U.S. stock market overnight, fueled by AI-related news. Meta’s “Muse,” a personal productivity Agent AI launched earlier this month, topped the free app rankings on the U.S. Apple App Store, fueling expectations that the proliferation of Agent AI agents would drive increased demand for central processing units (CPUs) and servers. Consequently, U.S. semiconductor stocks such as Intel and Arm surged, and buying interest also flowed into domestic semiconductor stocks.
However, investor sentiment cooled again as international oil prices rebounded during the trading session. West Texas Intermediate (WTI) crude oil futures, which had fallen to the $91 range on expectations of a diplomatic resolution between the U.S. and Iran, rose to $93.66 per barrel around 3:30 p.m., the close of the regular trading session on the Korean stock market. While the decline in oil prices early in the session acted as a positive factor for the stock market, the pressure increased again as prices partially recovered their intraday losses.
Lee Kyung-min, an analyst at DaishinSecurities, explained, “As WTI futures, which had fallen to $91, rebounded, the domestic stock market showed a pattern of strong gains early on followed by weakness later in the session.” He added, “Oil prices fell as expectations for an easing of geopolitical tensions emerged following hopes for a meeting between President Trump and Iranian President Pezeshkian, but a technical rebound resulting from the sharp short-term decline weighed on the stock market.”
◇Samsung Electronics Rises, SK Hynix Falls… Did Supply and Demand Diverge Ahead of Special Dividends?
SamsungElectronics and SK hynix, the “top two” semiconductor companies, which had risen together by around 3% early in the session, narrowed their gains during the trading day and closed with mixed results. SamsungElectronics(005930)closed at 276,500 won, up 2,500 won (0.91%) from the previous trading day, while SK hynix(000660)gave up all its gains, turned negative, and closed at 1.84 million won, down 28,000 won (1.50%).
While the supply-and-demand dynamics for both stocks were similar—with retail investors selling and “other corporations” buying due to share buybacks—foreign and institutional investors took opposite stances. According to the Korea Exchange, retail investors net sold SamsungElectronics and SK hynix shares worth 790.9 billion won and 436.3 billion won, respectively, while “other corporations” net bought 510.9 billion won and 1.1281 trillion won worth of shares, respectively. In contrast, foreign investors and institutions were net buyers of SamsungElectronics and SK hynix by 209.1 billion won and 70.9 billion won, respectively, while they were net sellers of SK hynix by 400.9 billion won and 290.9 billion won, respectively. This divergence in supply and demand among foreign and institutional investors is believed to have contributed to the contrasting price trends of the two stocks.
In particular, analysts suggest that dividend demand ahead of this month’s dividend record date played a partial role in the buying pressure from foreign and institutional investors on SamsungElectronics. A securities industry official stated, “SamsungElectronics’ dividend record date is September 30, so investors must hold the stock until the 28th to receive the special dividend,” adding, “It appears that demand driven by the dividend also influenced the difference in supply and demand compared to SK hynix.”
In addition, the top market-cap stocks on the KOSPI showed mixed performance. SamsungElectronics(1P)(005935)rose 1.68%, while SKSQUARE(402340)(0.53%) and HyundaiMotor(005380)(0.42%) also gained. SamsungElectroMechanics(009150)rose 3.99%, showing relative strength. On the other hand, KB Financial Group(105560)fell 1.01%, and SAMSUNG BIOLOGICS(207940)(-0.78%), LG Energy Solution(373220)(-0.43%), and SAMSUNG C&T CORPORATION(028260)(-0.14%) also declined. Samsung Life Insurance(032830)closed flat.
The KOSDAQ also gave up all of its early gains and closed lower. The KOSDAQ Index closed at 834.38, down 1.89 points (0.23%) from the previous trading day. The index opened at 846.14, up 9.87 points (1.18%) from the previous close, and rose as high as 847.10 during the session, but later turned bearish and briefly fell to 831.13.
In the KOSDAQ market, retail investors were net buyers of 156.4 billion won, while foreign and institutional investors were net sellers of 57.4 billion won and 95.2 billion won, respectively.
Among the top market-cap stocks, Alteogen Inc.(196170)closed at 249,500 won, down 5,500 won (2.16%) from the previous trading day, while ECOPRO CO., LTD(086520)closed at 80,100 won, up 200 won (0.25%).
ECOPRO BM CO., LTD.(247540) WONIK IPS Co.,Ltd.(240810) rose by 0.87% and by 1.01%, while fell by 0.97%, by 0.34%, by 2.17%, by 1.96%, and by 0.73%. surged by 13.31%, and soared by 7.45%. JUSUNG ENGINEERING Co.,Ltd.(036930) Rainbow Robotics(277810) EO Technics Co., Ltd.(039030) ROBOTIS(108490) HPSP Co., Ltd.(403870) SIMMTECH Co., Ltd.(222800) LEENO Industrial Inc(058470)