KOSPI and KOSDAQ Slide on Heavy Foreign Selling as Tech and Security Sectors Rally

The South Korean stock market closed sharply lower on September 11, 2026, with the benchmark KOSPI dropping 1.76% to 6,909.91 and the tech-heavy KOSDAQ falling 1.95% to 820.64. Heavy selling pressure dominated the session as foreign investors net-sold 2,291,481 million KRW in KOSPI and 312,023 million KRW in KOSDAQ, while the USD/KRW exchange rate finished at 1,339.00.

SamwhaCapacitor (001820) +18.76%

SamwhaCapacitor surged 18.76% on September 11, driven by the accelerating demand for artificial intelligence (AI) and automotive Multi-Layer Ceramic Capacitors (MLCC) [3]. Investors reacted to growing concerns over potential MLCC supply shortages fueled by the rapid expansion of AI and Energy Storage Systems (ESS) [6]. The stock rose to an intraday high of 137,700 KRW, up 19.01% [4], continuing its upward momentum from earlier in the week [1]. While the stock had previously dropped 4.28% on September 8 [5], the specific reason for that decline remains unconfirmed.

HD HYUNDAI HEAVY INDUSTRIES (329180) +5.62%

HD Hyundai Heavy Industries gained 5.62% following its massive 1 trillion KRW investment plan for engine facility expansion and Small Modular Reactors (SMR) [8][9][12]. Analysts noted that despite this large-scale investment, the stock's recent decline was an 'obvious undervaluation,' boosting investor sentiment [8][9][10][11]. This positive outlook, coupled with general strength across the shipbuilding sector, drove the stock higher [12]. This recovery follows a 2.16% drop on September 10 [7].

AXGATE Co., Ltd. (356680) +29.94%

Security software developer AXGATE hit the 29.94% daily limit-up to close at 16,060 KRW [14]. The rally was triggered by Nvidia CEO Jensen Huang's remarks identifying security as the next key market for artificial intelligence [15]. This statement, combined with rising concerns over sophisticated AI-driven hacking, fueled a broader rally across information security themes [16][18]. While the stock locked in a limit-up finish [13][17], specific company-level contracts or performance details behind the surge remain unconfirmed.

HankookCosmeticsManufacturing (003350) +19.38%

Hankook Cosmetics Manufacturing jumped 19.38% due to strong supply-demand dynamics, including simultaneous net buying by foreign and institutional investors [20]. Institutional investors extended their net buying streak to five consecutive days [22]. The intense buying pressure triggered volatility interruption (VI) mechanisms twice during the day as the stock surged up to 21.81% intraday [19][21]. Despite the strong market flows, the fundamental corporate developments or business catalysts driving this sudden influx of institutional and foreign capital remain unconfirmed.

KEPCO Engineering & Construction (052690) +4.83%

KEPCO Engineering & Construction rose 4.83% amid strong expectations surrounding a massive 120 billion USD nuclear power plant construction project in the United States [24][29]. The upward momentum was further supported by simultaneous net buying from foreign and institutional investors [27], which previously triggered a volatility interruption (VI) on September 8 [28]. Although the stock experienced a temporary 4.89% intraday drop on September 10 [25], the exact cause of that brief decline remains unconfirmed.

Sources

1. 삼화콘덴서 주가, 9월 9일 장중 116,700원 4.48% 상승 — 톱스타뉴스 · 2026-09-09
2. 삼화콘덴서 주가, 급등세... 왜? — 금강일보 · 2026-09-11
3. AI·전장용 MLCC 특수 본격화… 삼화콘덴서·코칩 주가 폭등랠리 — pinpointnews.co.kr · 2026-09-11
4. 삼화콘덴서 주가, 9월 11일 장중 137,700원 19.01% 상승 — 중앙이코노미뉴스 · 2026-09-11
5. 삼화콘덴서 주가, 9월 8일 111,700원 4.28% 하락 마감 — 톱스타뉴스 · 2026-09-08
6. [특징주] 삼화콘덴서, AI·ESS발 MLCC 공급 부족 우려에 19%대 급등 — 와이드경제 · 2026-09-11
7. HD현대중공업 주가, 9월 10일 453,500원 2.16% 하락 마감 — 톱스타뉴스 · 2026-09-10
8. [애널픽] HD현대중공업, 1조 투자에도 주가 하락…"현저한 저평가" — 뷰어스 · 2026-09-11
9. “엔진·SMR에 1조 쏟아붓는 HD현대중공업…주가 하락은 ‘명백한 저평가’” — 뉴스퀘스트 · 2026-09-11
10. [리포트 브리핑]HD현대중공업, '드디어 엔진 증설, 저평가된 주가 ' 목표가 860,000원 - iM증권 — 뉴스핌 · 2026-09-10
11. 2026.09.11.(금) 증권사리포트 "HD현대중공업 - 드디어 엔진 증설, 저평가된 주가" — 네이버 프리미엄콘텐츠 · 2026-09-11
12. HD현대중공업, 엔진·SMR 투자 기대 5%↑…조선주 강세[핫종목] — 뉴스1 · 2026-09-11
13. 엑스게이트 주가, 상한가... 왜? — 금강일보 · 2026-09-11
14. 엑스게이트 주가, 9월 11일 16,060원 29.94% 상한가 마감 — 톱스타뉴스 · 2026-09-11
15. [ET특징주] 젠슨황 “AI 다음 핵심 시장은 '보안'”… 샌즈랩 · 엑스게이트 上 — etnews.com · 2026-09-11
16. 해킹도 AI로 고도화…엑스게이트·샌즈랩·드림시큐리티 주가 '불기둥' — pinpointnews.co.kr · 2026-09-11
17. [급등주] 엑스게이트, +29.94% 상한가 기록 — jeonmae.co.kr · 2026-09-11
18. 특징주, 엑스게이트-정보보안 테마 상승세에 3.44% ↑ — 매일경제 마켓 · 2026-09-11
19. [속보] 한국화장품제조 VI 두차례 발동, 주가 급등 — CBC뉴스 · 2026-09-11
20. [장중수급포착] 한국화장품제조, 외국인/기관 동시 순매수… 주가 +18.62% — 뉴스핌 · 2026-09-11
21. 한국화장품제조 주가, 9월 11일 장중 16,030원 21.81% 상승 — 중앙이코노미뉴스 · 2026-09-11
22. [장중수급포착] 한국화장품제조, 기관 5일 연속 순매수행진... 주가 +4.71% — 뉴스핌 · 2026-09-11
23. 한국화장품제조, 주주 타이거자산운용투자일임 측 주식등 보유 비율 5.28%p 감소 — 디지털투데이 · 2026-09-10
24. 한전기술 주가 장중 5%대 상승, 미국 대형 원전 건설 기대감 — 비즈니스포스트 · 2026-09-09
25. 한전기술 주가, 9월 10일 장중 136,100원 4.89% 하락 — 톱스타뉴스 · 2026-09-10
26. 수주 근거는 두산, 주가는 한전기술…원전 수혜株는 어디로 — 메트로신문 · 2026-09-09
27. [장중수급포착] 한전기술, 외국인/기관 동시 순매수… 주가 +16.52% — 뉴스핌 · 2026-09-08
28. [속보] 한전기술 VI 발동, 주가 장초반부터 급등 — CBC뉴스 · 2026-09-08
29. 한전기술 주가 12%대 상승, 1200억 달러 규모 미국 원전 건설 기대감 반영 — 비즈니스포스트 · 2026-09-08

This is market commentary, not investment advice.