verdict at the close
KOSPI sheds 2.65% to 6,792.93; KOSDAQ off 4.23%
Korean equities closed sharply lower on Tuesday, August 18 (2026): the KOSPI finished at 6,792.93, down 2.65%, while the KOSDAQ fell 4.23% to 828.05.The KOSPI printed an intraday range of 427.84 points (6.3% high-to-low), touching a session high of 7,216.62 at 09:39 before sellers took over through the afternoon; multiple investor groups weighed simultaneously, and no single cause can be isolated.
The day’s path
A window marking the hours when direction turned during the session
KOSPI traced a 6.3% intraday arc — peak at 09:39, trough at 15:08 — before closing at 6,792.93, down 2.65%.
Top by trading value10— snapshot
A window on how the top trading-value names have moved up to this hour
KOSPI high of 7,216.62 at 09:39 gave way to a sustained slide; SK hynix held the top turnover spot through the close.
| Stock | Prior close | Open | Gap | High (time) | Close | Change | Low (time) |
|---|---|---|---|---|---|---|---|
| SK hynix | 1,645,000 | — | — | — | 1,662,000 | +1.03% | — |
| Samsung Electronics | 274,500 | — | — | — | 268,500 | −2.19% | — |
| Samsung Electro-Mechanics | 1,558,000 | — | — | — | 1,440,000 | −7.57% | — |
| SK Square | 1,154,000 | — | — | — | 1,135,000 | −1.65% | — |
| Samsung Electronics (Pref.) | 195,600 | — | — | — | 188,300 | −3.73% | — |
| Hyundai Motor | 453,000 | — | — | — | 435,000 | −3.97% | — |
| LG Electronics | 215,000 | — | — | — | 208,000 | −3.26% | — |
| Samsung SDI | 516,020 | — | — | — | 488,000 | −5.43% | — |
| SK eternix | 58,300 | — | — | — | 58,500 | +0.34% | — |
| LG Innotek | 653,993 | — | — | — | 633,000 | −3.21% | — |
The KOSPI reached its intraday peak of 7,216.62 at 09:39 before turning lower, with the decline steepening after 10:40 and the index touching its session trough of 6,788.78 at 15:08; a partial recovery into the close left the index at 6,792.93 on the confirmed print.SK hynix retained the top spot by KOSPI turnover at ₩877.3bn through the session, with Samsung Electronics second at ₩660.7bn; on the NXT (Nextrade)Korea’s alternative trading system, launched in 2026, that operates a pre-market, a main session, and an after-market alongside the KRX main exchange.NXT data — shown here on a 20-minute delay — give an early read on breadth and turnover before KRX official figures are published. alternative exchange, SK hynix also led at ₩5,085.5bn (NXT snapshot, 20-minute delayed as of 15:33) — those are NXT-only figures and not directly additive to KRX main-market data.
Flow summary
A window on how much foreign investors, retail investors, investment firms and pension funds each bought and sold
Institutional selling of ₩785.3bn overwhelmed foreign net buying of ₩91.4bn on the KOSPI, as the index dropped 2.65% to close at 6,792.93.
The stocks that moved the market — top by turnover10
A window on which investor groups backed the most heavily traded stocks
SK hynix led KOSPI turnover at ₩877.3bn and closed up 1.03%, while Samsung Electro-Mechanics was the session’s most-traded decliner, falling 7.57% on ₩1,625.5bn in volume.
SK hynix (₩877.3bn turnover, +1.03%) was the day’s most-traded name on the KOSPI and the only member of the top two by volume to close in positive territory; Samsung Electronics, the second-most-active at ₩660.7bn, fell 2.19%.Samsung Electro-Mechanics (₩1,625.5bn, −7.57%) ranked third by volume and was the steepest decliner among the KOSPI top ten; on the KOSDAQ side, Jusung Engineering (₩423.0bn, +0.84%) and HPSP (₩289.1bn, +5.57%) were among the few advancers in that market’s top-ten list.
| Stock | Close | Change | Turnover | Foreign investors | Institutions | Investment firms | Pension funds | Retail investors |
|---|---|---|---|---|---|---|---|---|
| SK hynix | ₩1,662,000 | +1.03% | ₩8.77tn | +₩790.9bn | −₩123.6bn | −₩281.5bn | +₩120.9bn | −₩646.3bn |
| Samsung Electronics | ₩268,500 | −2.19% | ₩6.61tn | +₩176.7bn | −₩247.6bn | −₩215.2bn | −₩28.4bn | +₩83.9bn |
| Samsung Electro-Mechanics | ₩1,440,000 | −7.57% | ₩1.63tn | −₩418.7bn | −₩168.7bn | −₩57.3bn | −₩60.0bn | +₩582.4bn |
| SK Square | ₩1,135,000 | −1.65% | ₩845.3bn | +₩49.7bn | −₩35.9bn | −₩10.3bn | −₩12.4bn | −₩10.0bn |
| Samsung Electronics (Pref.) | ₩188,300 | −3.73% | ₩842.5bn | −₩188.2bn | +₩7.9bn | +₩2.6bn | −₩8.7bn | +₩175.5bn |
| Hyundai Motor | ₩435,000 | −3.97% | ₩383.7bn | −₩82.0bn | +₩1.3bn | −₩2.9bn | +₩0.2bn | +₩80.3bn |
| LG Electronics | ₩208,000 | −3.26% | ₩329.2bn | −₩27.4bn | −₩12.9bn | −₩22.5bn | +₩7.6bn | +₩39.7bn |
| Samsung SDI | ₩488,000 | −5.43% | ₩243.2bn | −₩35.1bn | −₩8.7bn | −₩4.8bn | −₩0.5bn | +₩44.2bn |
| SK eternix | ₩58,500 | +0.34% | ₩230.9bn | −₩11.6bn | +₩11.1bn | +₩2.6bn | +₩2.6bn | −₩0.4bn |
| LG Innotek | ₩633,000 | −3.21% | ₩215.2bn | −₩52.3bn | −₩11.7bn | −₩13.9bn | −₩1.0bn | +₩65.8bn |
Gainers5· Decliners5 — KOSPI & KOSDAQ
A window on the biggest gainers and decliners, and the reasons behind them
Broad-based selling pushed the KOSDAQ down 4.23% to 828.05, with decliners on the NXT snapshot outnumbering advancers 512 to 84.
Among KOSPI names with at least ₩100bn in turnover, decliners dominated: Samsung Epis Holdings led losses at −11.30%, followed by Samsung Electro-Mechanics preferred at −8.48% and CJ at −8.11%, while Hyundae Haesang and Samah Aluminum posted gains of +9.59% and +9.64% respectively.On the KOSDAQ, Injenia Therapeutics (Reg.S) surged +49.92% on ₩715.5bn in turnover — by far the day’s most active KOSDAQ name — while Aurora plunged −26.16% and Bonne fell −23.22%; the NXT snapshot at 15:33 showed 512 decliners against 84 advancers across 608 listed names, indicating breadth was heavily skewed to the downside.
After-Hours Outlook
A window on what to watch in after-hours trade once the regular session ends
Session closed deep in the red; post-market activity will be watched against a backdrop of U.S. 30-year yields at 5.31% and weak overnight futures.
In the 2026 regime (n=31 Tuesdays), the KOSPI has risen on 71% of Tuesdays with an average move of +0.19%; today’s confirmed −2.65% outcome sits well outside the regime’s typical Tuesday range, which may draw attention to Wednesday’s session — in the 2026 regime, Wednesdays have shown a 80% advance rate (n=30) with an average gain of +1.14%, though past rates are not guarantees of direction.The pre-close sell-side bias was visible in non-arbitrage program net selling of ₩1,088.7bn; in the current regime (2026), short-surge events in the prior five sessions (SK hynix surge ratio 0.01×–0.02×, Simtech 2.4×–2.8×) have shown mixed five-day outcomes, averaging −0.50% with a 51% down-probability across 111 events in the current regime — the judgment on direction is each reader’s own.