[Edaily Reporter kyoungeun kim ] On the 23rd, the KOSPI closed up more than 4% as expectations grew that companies would benefit from artificial intelligence (AI) infrastructure following confirmation of Alphabet’s capital expenditure (CapEx) guidance.

With the market’s undervaluation relative to earnings forecasts coming into focus, foreign investors have been making large-scale net purchases for four consecutive trading days. The KOSDAQ, which had been struggling below the 800-point mark, rose by over 5% during the session—recovering to the 790-point level—as the intraday “buy-side car” mechanism was triggered, driven by strength in secondary battery and biotech stocks.
According to MP Doctor, the KOSPI closed at 7,096.89, up 299.19 points (4.40%) from the previous trading day. The index briefly rose to 7,108.44 during the session, breaking through the 7,100 mark.
On the day, 831 stocks rose and 74 fell, with buying interest spreading evenly across all sectors, moving beyond the previous reliance on semiconductors.
Alphabet’s Google Cloud revenue surged 82% year-over-year, significantly exceeding expectations, and the company raised its annual capital expenditure forecast to a maximum of $205 billion, fueling expectations that the entire AI infrastructure sector—including semiconductors—would benefit.
On the KOSPI market, foreign investors led the index higher with net purchases of 2.1351 trillion won. Institutional investors also showed a net buying position of 101.1 billion won. In contrast, retail investors showed a net selling position of 2.2107 trillion won. Program trading, combining arbitrage and non-arbitrage trades, recorded a net purchase of 1.7574 trillion won.
Including trading volume on alternative exchanges, foreign investors have made net purchases of approximately 7.1 trillion won over the past four trading days, signaling a shift away from their previous selling trend.
Most of the top market-cap stocks closed sharply higher. LG Energy Solution(373220)(+8.41%), SamsungElectroMechanics(009150)(+7.66%), SK hynix(000660)(+4.86%), SamsungElectronics(005930)(+3.65%), SamsungElectronics(1P)(005935)(+3.24%), HyundaiMotor(005380)(+3.35%), Samsung Life Insurance(032830)(+2.97%), SAMSUNG BIOLOGICS(207940)(+0.51%), and KB Financial Group(105560)(+0.69%) all rose. In contrast, SKSQUARE(402340)closed down 9,000 won (0.73%).
The KOSDAQ index closed at 790.28, up 39.19 points (5.22%). Foreign and institutional investors were net buyers of 133 billion won and 60.3 billion won, respectively, while retail investors were net sellers of 198.5 billion won. There were 1,442 gainers and 252 losers.
The Korea Exchange triggered a buy-side circuit breaker on the KOSDAQ market at 2:27 p.m. that day. This was due to the KOSDAQ 150 futures (nearest month) reaching 1,341.50 points—a 6.29% increase from the previous day’s closing price (1,262.00 points)—while the KOSDAQ 150 Index itself rose 5.27% to 1,333.63 points compared to the previous day’s closing price(1,266.85 points) to 1,333.63 points, and this upward trend persisted for one minute. This marks the 24th time a sidecar has been triggered this year and the 14th time a buy-side sidecar has been activated.
Most of the top KOSDAQ stocks by market capitalization closed higher. With the market-cap leader, Alteogen Inc.(196170)(+14.37%), surging sharply, optimism spread across secondary battery and biotech stocks in general. ECOPRO BM CO., LTD.(247540)(+9.95%), ECOPRO CO., LTD(086520)(+9.34%), ABL Bio Inc.(298380)(+7.06%), EO Technics Co., Ltd.(039030)(+6.48%), Rainbow Robotics(277810)(+6.17%), LEENO Industrial Inc(058470)(+2.92%), JUSUNG ENGINEERING Co.,Ltd.(036930)(+1.17%), and WONIK IPS Co.,Ltd.(240810)(+1.43%) all rose. PSK INC.(319660)(+0.19%) closed slightly higher.