KOSPI Gains 0.90% Before Chuseok as Chips and Medical AI Lead Selectively

South Korean equities entered the Chuseok break with gains, but the headline return overstated the breadth of the large-cap recovery. On September 23, 2026, the KOSPI closed at 7,080.92, up 0.90%, while the KOSDAQ gained 1.21% to 844.48. The useful distinction is between semiconductor support for the main index and selective buying further down the market.

A positive close with uneven participation

The KOSPI opened 1.94% higher and surrendered part of that advance. Foreign investors turned net sellers, alongside individuals, while institutions and other corporate accounts bought. We use flow direction rather than amounts because the available snapshots differ in timing and classification. Corporate buying should not automatically be treated as evidence of a broader institutional allocation to Korea.

Hankyung’s market snapshot around the close showed more decliners than advancers on the KOSPI, whereas advancers outnumbered decliners on the KOSDAQ. KSI therefore reads the session as a concentrated large-cap rebound with some expansion into smaller growth companies. It does not yet establish that the typical Korean stock is participating in a durable recovery.

Memory and equipment: related themes, different earnings tests

Samsung Electronics rose 3.25% and SK hynix gained 1.20%. The overnight US backdrop was supportive: Micron advanced 5.00% and the Philadelphia Semiconductor Index rose 2.06%. That helped sustain expectations for AI-related memory demand. The transmission to Korean earnings still depends on customer spending, shipments and pricing; a US share-price move is not a new Korean supply contract.

Buying also reached semiconductor equipment. EXICON finished at KRW 42,950, up 13.03%, below its intraday high of KRW 45,600. Wonik IPS gained 2.61%. These moves support a second focus on testing and process equipment, but they do not imply identical earnings cycles. Orders, delivery schedules and margins will determine whether enthusiasm for customer investment becomes profitable revenue. The retreat from EXICON’s high also matters when judging the strength of follow-through.

Medical AI: a research opportunity is not booked sales

3billion closed at KRW 5,800, up 23.27%. Its September 22 announcement identified the company as a participant in a KAIST-led rare-disease research project. The overall consortium project can receive up to KRW 8 billion over July 2026 through December 2030. That figure is neither revenue awarded entirely to 3billion nor a commercial drug order.

KSI sees a potential extension of the company’s genomic analysis capabilities into therapeutic research. Participation nevertheless leaves substantial execution and commercialization work ahead. The announcement provides relevant context rather than proof of the sole cause of the rally. Investors should separately assess whether paying customers for diagnostic and analytical services translate into earnings and cash generation.

What would make the recovery more convincing?

The dollar stood at KRW 1,358.4 at 15:30 KST, up KRW 0.2, so a stronger won was not the day’s supporting explanation. Cash equities reopen on September 28 after the holiday and weekend. The September 23 derivatives night-session closure is separate from the cash session completed today.

The next test combines three observations: semiconductor leaders retaining their gains, foreign buying returning, and more KOSPI constituents advancing. US chip performance, oil and currency developments during the break may be reflected together when Korea reopens. Equipment orders and medical-AI commercialization deserve their own checks. A higher index with shrinking participation would retain the same concentration risk; improving flows and breadth together would provide firmer evidence of a sustainable recovery.

Key Data Sources

• 연합뉴스 — 코스피 63.01p(0.90%) 오른 7,080.92 장종료
• 연합뉴스 — 코스닥 10.10p(1.21%) 오른 844.48 장종료
• YTN — 코스피·코스닥 상승 마감 및 15:30 환율
• 한국경제 — 추석 앞둔 코스피, 관망심리에 오름폭 축소
• 한국경제 — 코스피 시장지표 및 등락 분포
• 한국경제 — 코스닥 시장지표 및 등락 분포
• 머니투데이 — 미국 기술주 강세와 반도체 중소형주 장초반 동향
• 한국경제 — 엑시콘 2026-09-23 장마감 시세
• 한국경제 — 쓰리빌리언 2026-09-23 장마감 시세
• 쓰리빌리언 — 쓰리빌리언 ARPA-H ARISE 공동연구 참여
• 뉴스핌 — 추석 전날 야간 파생시장 휴장 안내