Seoul — September 28, 2026. Published after the market close. Stock and index prices are official closing values; FX and bond-yield figures are time-specific market readings, not official closes.
The 30-second version
- The KOSPI fell 2.70% to 6,889.74 in its first session after the Chuseok holiday, giving back the 7,000 level just four sessions after reclaiming it.
- The trigger: US Treasury yields surged while Korea was on holiday. The 30-year touched 5.519% intraday — its highest since June 2004 — and finished the period at 5.52%.
- Foreign investors net sold about 3.60 trillion won (roughly $2.6 billion) of KOSPI shares and institutions another 1.33 trillion won (about $1.0 billion); retail investors bought 3.29 trillion won (about $2.4 billion) but could not hold the line.
- Semiconductors led the damage: Samsung Electronics fell 5.43% and SK hynix 5.05%, dragging the electronics sector down 4.46%.
- The KOSDAQ went the other way, up 0.25% to 846.58, as seven HLB group stocks hit or neared Korea’s 30% daily price limit after a US FDA drug approval.
- The won firmed modestly, with USD/KRW quoted around 1,360 late in the session, in a choppy day caught between quarter-end exporter dollar selling and foreign equity outflows.
A holiday hangover, delivered by the US bond market
Korean markets were shut for Chuseok, Korea’s autumn harvest holiday, while the rest of the world kept trading — and what the world traded was bad news for rate-sensitive stocks. A run of firm US economic data and hawkish comments from Federal Reserve officials pushed Treasury yields sharply higher during the break. The 30-year yield touched 5.519% at one point, its highest since June 2004, with the curve finishing the period at 4.91% on the 2-year, around 5.2% on the 10-year and 5.52% on the 30-year.
When Seoul reopened on Monday, it had to digest all of that in a single session. The KOSPI actually opened higher at 7,057.86 and briefly reached 7,065.90, but selling built through the afternoon and the index slid to an intraday low of 6,889.68 before closing at 6,889.74, down 2.70%.
Why do US yields matter this much in Seoul? Two reasons. Higher long-term rates shrink the present value of future profits, which hits growth-heavy chipmakers hardest. And a 5%-plus Treasury yield gives global funds a low-risk alternative to holding Korean equities at all. Foreign investors acted accordingly, dumping a net 3.60 trillion won of KOSPI shares, with institutions selling another 1.33 trillion won — concentrated in the semiconductor giants. Samsung Electronics fell 5.43% to 270,000 won and SK hynix 5.05% to 1,768,000 won, while SK Square (-7.56%) and Samsung C&T (-5.86%) also slumped. Notably, genuinely positive headlines from the break — a US-China leaders’ meeting and signs of easing US-Iran tensions — were simply swallowed by the rate move, as local coverage put it.
HLB’s FDA first turns the KOSDAQ green
The small-cap KOSDAQ told a completely different story. During the holiday, Elevar Therapeutics, the US subsidiary of KOSDAQ-listed biotech HLB, received FDA approval for Rivfitu, a treatment for biliary tract (bile duct) cancer. Local coverage describes it as the first time a Korean pharmaceutical or biotech company has directly filed a global oncology new-drug application with the FDA and won approval.
A quick mechanics note for readers new to Korea: stocks here cannot move more than 30% in either direction in a single day. Reaching that ceiling is called “limit-up” — think of it as a price fuse that stops a stock from trading any higher that session. Seven HLB-affiliated names hit or came within a whisker of it: HLB Pharmaceutical (+30.00%), HLB Bio Step (+30.00%), HLB Life Science (+29.96%), HLB itself (+29.95%), HLB Panagene (+29.95%), HLB Therapeutics (+29.84%) and HLB Genex (+29.83%).
That rally, plus modest net buying on the KOSDAQ from both retail investors (+21.8 billion won) and foreigners (+35.7 billion won) against institutional selling (-69.0 billion won), was enough to nudge the index up 0.25% to 846.58. It was a stock picker’s tape otherwise: Remedi jumped around 24%, while Pintel (-18.42%), Hanju ART (-17.92%) and FromBio (-17.51%) fell hard with no confirmed disclosures explaining the drops.
The other side of the tape: chemicals, construction, solar
Even on the KOSPI, this was a divergence day rather than an everything-selloff. Chemicals (+3.20%) and construction (+3.05%) topped the sector table. Hanwha Solutions jumped 10.62% to 32,300 won on expectations of rising solar module prices in the US, where the company operates production facilities. Construction rallied behind Daewoo E&C (+7.57%, at 18,760 won) and Kumkang Kind (+18.9%). Textiles and apparel (+1.43%), pharmaceuticals (+1.19%) and electricity-and-gas utilities (+1.11%) also gained, while retail (-2.82%), machinery (-0.60%) and medical-precision equipment (-0.52%) fell alongside electronics. Among large caps, LG Energy Solution (+3.56%), Samsung Biologics (+2.49%) and KB Financial (+0.58%) stayed green — evidence this was a rates-and-chips selloff, not indiscriminate liquidation.
The won had a choppy session of its own, tugged between quarter-end dollar selling by exporters and foreign investors converting the proceeds of their stock sales. Late in the session, USD/KRW traded around 1,360, down modestly on the day.
| Measure | Level | Change |
|---|---|---|
| KOSPI | 6,889.74 | -191.18 (-2.70%) |
| KOSDAQ | 846.58 | +2.10 (+0.25%) |
| USD/KRW | around 1,360 | down modestly (late-session quote) |
| Samsung Electronics | 270,000 won | -5.43% |
| SK hynix | 1,768,000 won | -5.05% |
| US 10-year Treasury yield | around 5.2% | holiday-period level |
| US 30-year Treasury yield | 5.52% | touched 5.519% intraday, highest since June 2004 |
What to watch next
- US PCE inflation data this week — the key input for Fed expectations after the hawkish holiday repricing.
- Micron earnings — a direct read-through for Samsung Electronics and SK hynix, today’s biggest casualties.
- US nonfarm payrolls — strong data helped drive yields up; another hot print would extend the pressure.
- Foreign flows — whether the 3.6-trillion-won single-day sale of KOSPI shares was a one-off repricing or the start of a trend.
- USD/KRW around quarter-end — exporter dollar sales and equity outflows are pulling in opposite directions.
FAQ
Why did the KOSPI fall 2.7% on September 28, 2026?
It was the first session after the Chuseok holiday, and the market had to price in a holiday-week surge in US Treasury yields — the 30-year hit its highest level since June 2004. Foreign and institutional investors sold nearly 5 trillion won of KOSPI shares combined, concentrated in semiconductor heavyweights, and retail buying of 3.29 trillion won could not offset it.
Why did HLB stocks hit the daily limit?
During the holiday, HLB’s US subsidiary Elevar Therapeutics won FDA approval for Rivfitu, a biliary tract cancer drug — reported as the first FDA approval of a global oncology NDA filed directly by a Korean company. Seven HLB group stocks closed at or just under the +30% cap.
What does “limit-up” mean in the Korean stock market?
Korean exchanges cap single-day price moves at plus or minus 30%. A stock that rises the full 30% is “limit-up” and cannot trade any higher that day.
Why did the KOSDAQ rise while the KOSPI fell?
The KOSPI is dominated by the large exporters and chipmakers that foreign investors sold on rate fears. The KOSDAQ is a smaller-cap market that got a concentrated boost from the HLB group rally, alongside modest net buying from both retail and foreign investors on that exchange.
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: Foreign Investors Sold Samsung and SK Hynix as US Yields Spiked.