Seoul — September 29, 2026. Published after the market close; index and stock prices are official closing values, while currency and commodity figures are market quotes as of the times noted.
The 30-second version
- The KOSPI fell 0.27% to 6,870.81 — its second straight decline — after sliding as low as 6,782.99 intraday and clawing most of it back by the close.
- Foreign investors net sold 2.90 trillion won (roughly $2.1 billion) of KOSPI shares, the dominant force behind the drop. Retail investors bought 1.14 trillion won against them.
- The KOSDAQ went the other way, closing up 0.38% at 849.80 on retail buying.
- The trigger came from abroad: the US 10-year Treasury yield jumped above 5.21% overnight, and WTI crude ended the September 28 US session at $92.60 amid the Iran-Hormuz standoff.
- Construction was the worst sector at -5.38%; leveraged battery ETFs fell more than 7%.
- The won weakened slightly, with the dollar quoted around 1,357 won late in the Seoul session (the 3:30pm local indicative quote traded around 1,356.7).
A $2.1 billion foreign exit — and why it happened
The setup was ugly before Seoul even opened. Overnight, all three major US indexes fell — the Dow lost 0.7% to 51,481.51, the S&P 500 dropped 0.8% to 7,683.69, and the Nasdaq slid 0.9% to 26,820.38 — as the 10-year Treasury yield pushed above 5.21% and oil kept climbing. Nasdaq 100 night futures were down 0.92% heading into the Korean open, so a weak start was no surprise.
Higher US yields hurt Korean equities in two ways. They compress valuations everywhere (a stock’s future earnings are worth less when the risk-free rate is above 5%), and they pull global capital toward dollar assets. Both effects showed up in one line item today: foreign investors dumped a net 2.90 trillion won — about $2.1 billion at today’s exchange rate — of KOSPI shares. Coming one day after a drop of more than 2%, that selling pushed the index as low as 6,782.99 during the session.
The close tells a more resilient story, though. Retail investors net bought 1.14 trillion won (about $840 million) and institutions added a modest 121.1 billion won, absorbing enough of the foreign supply that the KOSPI finished down just 0.27%. Foreign investors hold a large share of Korea’s biggest companies, so when they sell in size the index moves — but domestic buyers stepped in front of the wave today and largely held the line.
The tape: defense and chip suppliers up, construction and batteries hit
Defense (+2.50%) and biosimilar (+2.34%) themes topped the leaderboard, and semiconductor equipment and materials names were strong — SemiFive jumped 18.40%, with DB HiTek and HPSP also gaining. The mega-cap chipmakers themselves were mixed: Samsung Electronics added 0.93% to 272,500 won while SK hynix slipped 0.17% to 1,765,000 won.
Three small caps — C-Cyte, LaMediTech and TeraView — closed “limit-up,” rising roughly 30%. Korean exchanges cap daily price moves at plus or minus 30% from the previous close; a stock at the ceiling can’t rise any further that day, though trading can continue at the limit price and the shares can still fall back below it. Hyundai Bioland (+18.21%) and Bowon Chemical (+16.55%) also ran hot.
The other side of the ledger was rough. The KOSPI construction sub-index sank 5.38%, the worst of any sector, with Hyundai E&C down 6.42% and GS E&C down 4.36% — a sharp one-day reversal for a group that had been riding AI-related infrastructure hopes. Batteries dragged too: LG Energy Solution fell 2.75-2.82% into the 350,000-won range, and the pain was amplified in leveraged products, with the KODEX secondary-battery leveraged ETF down 7.71% and its TIGER counterpart down 7.21%. (Leveraged ETFs aim to deliver a multiple of their index’s daily move — great on green days, punishing on red ones.) Casino (-2.43%) and travel and tourism (-2.42%) themes also lagged.
The KOSDAQ’s quiet divergence
While the KOSPI fought foreign selling, the KOSDAQ — Korea’s tech- and small-cap-heavy second market — quietly rose 0.38% to 849.80. The mechanics were simple: retail investors net bought 148.6 billion won (about $110 million), institutions chipped in 5.2 billion won, and foreign selling there was a comparatively small 129.1 billion won. Foreign money is concentrated in KOSPI large caps, so on days like this the two markets often split.
One footnote worth separating from the genuine theme flows: two IPOs debuted with fireworks. BigWave Robotics closed 167.78% above its offering price and Global Technology finished up roughly 156-168%. First-day pops of that size reflect short-term speculative demand for new listings, not a broader risk-on signal.
Key closing numbers
| Measure | Close | Change |
|---|---|---|
| KOSPI | 6,870.81 | -0.27% (-18.93 pts) |
| KOSDAQ | 849.80 | +0.38% (+3.22 pts) |
| USD/KRW | Quoted around 1,357 late in the September 29 Seoul session | +0.20% (won weaker; the 3:30pm indicative quote traded around 1,356.7) |
| Foreign net flow, KOSPI | -2.90 trillion won (~$2.1B) | Net sell |
| Retail net flow, KOSPI | +1.14 trillion won | Net buy |
| WTI crude (Nov contract) | $92.60 (September 28 US session, reflected overnight in Korea) | Higher on Hormuz risk |
| US 10-year Treasury yield | Above 5.21% | Sharply higher overnight |
| KOSPI construction sub-index | — | -5.38% (worst sector) |
What to watch next
- Foreign flows. Two straight down sessions with today’s 2.9 trillion won of selling — whether it extends or exhausts is the single biggest driver for the KOSPI’s next move.
- US rates. Whether the 10-year yield holds above 5.21% will set the valuation backdrop for Korean equities.
- Iran and the Strait of Hormuz. President Trump officially rejected Iran’s conditional reopening plan (“they proposed it, we refused”), but Qatar-mediated US-Iran talks are reportedly in the works — oil pared some intraday gains on that news before WTI ended the September 28 US session at $92.60.
- Construction and batteries. After outsized one-day drops, watch whether these groups stabilize or keep unwinding.
FAQ
Why did the KOSPI fall on September 29, 2026?
Foreign investors net sold 2.90 trillion won (about $2.1 billion) of KOSPI shares after the US 10-year Treasury yield spiked above 5.21% and oil prices rose. It was the index’s second consecutive decline, though retail and institutional buying limited the loss to 0.27%.
Why did the KOSDAQ rise while the KOSPI fell?
Retail investors net bought 148.6 billion won of KOSDAQ shares, and foreign selling — which was concentrated in KOSPI large caps — was much smaller there. That domestic bid was enough to lift the index 0.38%.
What does “limit-up” mean in the Korean stock market?
Korean exchanges restrict any stock’s daily move to plus or minus 30% from the prior close. A stock that hits the +30% ceiling is “limit-up” — it can’t rise any further that day, though trading can continue at the limit price and the stock can still trade back down. Three small caps — C-Cyte, LaMediTech and TeraView — hit that ceiling today.
How much did foreign investors sell in Korea today?
A net 2.90 trillion won (roughly $2.1 billion) on the KOSPI, plus a further 129.1 billion won on the KOSDAQ, per Korea Exchange closing data.
Disclaimer: This is an information and analysis publication, not investment advice. See our Methodology for data sources, standards, and our corrections policy.
Related reading
Also on Seoul Closing Bell
A companion piece on the same session, written from a different angle: KOSPI's 2.9 Trillion Won Foreign Sell-Off and Who Absorbed It.