KOSPI Gives Back Its Opening Rally as Substrates and Testing Stocks Stand Out

Korea failed to retain most of its opening rally on September 22, 2026. The KOSPI finished at 7,017.91, up 0.15%, after gaining more than 2% early in the session. The KOSDAQ slipped 0.23% to 834.38. For global investors, the useful signal was the gap between enthusiasm at the open and selective buying that survived the close. Source 1 Source 2

An AI tailwind met resistance

Optimism around Meta’s AI services and the US technology rally supported the opening move. Hankyung’s closing account identified a rebound in oil prices and selling by individuals as factors behind the subsequent loss of momentum. The KOSPI briefly fell below 7,000 before recovering that threshold. A positive closing index therefore masks a much weaker intraday trajectory. Source 11

Even the memory heavyweights diverged. Samsung Electronics closed at KRW 276,500, up 0.91%, while SK hynix fell 1.50% to KRW 1,840,000. This was insufficient evidence of a uniform revaluation of Korean semiconductor leaders. The distinction matters for index exposure, where a handful of large companies can obscure conditions elsewhere. Source 3

Participation remained narrow

Hankyung’s closing market snapshot showed institutions and foreigners buying the KOSPI on a net basis while individuals sold. In the KOSDAQ, individuals were net buyers against selling by both other groups. We use the direction of these provisional flows rather than potentially changing amounts. Decliners outnumbered advancers in both markets. Our interpretation is selective demand within AI-related businesses, with limited evidence of a broad recovery in risk appetite. Source 3 Source 4

Three areas retained relative strength

Semiconductor substrates and circuit boards: Korea Circuit gained 25.43%, Simmtech 13.31% and Samsung Electro-Mechanics 3.99%. MoneyToday’s intraday analysis linked interest in the group to AI infrastructure and expectations of a broader packaging-substrate supply chain. These returns are separately checked closing figures. The investment question now moves from demand expectations to actual deliveries, capacity utilization and margins. Source 3 Source 5 Source 8

Semiconductor testing components: LEENO Industrial rose 7.45% to KRW 75,000. The Korea IR Council describes a business supplying test sockets and pins used in semiconductor inspection. Its positive price response contrasted with SK hynix’s decline. That relative strength does not itself establish a new order or an earnings upgrade; shipment volumes and pricing still need to substantiate the opportunity. Source 6 Source 10

On-device AI for robotics: Nota closed at KRW 22,550, up 29.97%. Its September 18 technical publication describes reducing robotic-model inference latency from 1.6 seconds to 230 milliseconds on a Qualcomm NPU. This is a result from a specific demonstration setup. It supports the feasibility of local processing, but commercial deployment and recurring revenue require separate evidence. Source 7 Source 9

What would make the next advance more convincing?

KSI would look for three developments together: renewed agreement in the direction of Samsung Electronics and SK hynix, sustained closing strength in substrates and testing components, and better KOSDAQ institutional flows accompanied by more advancing stocks. Without broader participation, a defended index level offers only limited reassurance about the average stock.

A further oil-price rebound could again challenge the opening narrative. The stronger case for extending the rally would combine firm prices with verifiable orders and earnings, rather than treating every AI demonstration as immediate revenue. All stock returns in this article refer to the September 22 regular-session close.

Key Data Sources

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• 한국경제 — 코스피, 2%대 상승분 반납…7000선 가까스로 지켜
• 한국경제 — 코스피 수급·시장 폭·대형주 종가
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• 한국경제 — 심텍 9월 22일 종가
• 한국경제 — 리노공업 9월 22일 종가
• 한국경제 — 노타 9월 22일 종가
• 머니투데이 — 메타 효과와 기판 공급망 기대: 11시49분 장중 분석
• 노타 공식 기술 블로그 — GPU 없이 VLA 돌리기: 퀄컴 NPU 최적화
• 한국IR협의회 기업리서치센터 — 리노공업: 반도체 테스트 소켓 업체
• 한국경제 — 미 반도체주 급등에도 개인 매도와 유가 반등