[Today's Market] KOSPI Spikes to 6,579—Why Did Foreigners Pile Into Semiconductors When Retail Sold ₩3 Trillion?

Today (August 12, 2026), the KOSPI closed at 6,579.04, surging 3.68% (+233.51 points) from the previous day. To cut to the chase: the index's jump was driven by just two semiconductor stocks—Samsung Electronics and SK Hynix. Here's what's unusual: while foreigners poured ₩2.84 trillion into semiconductors, retail investors sold ₩3.19 trillion, yet the index still rallied 3.68%—an uncommon combination. Let me walk you through why.

KOSPI daily chart (Naver Finance)

Index and flows — cautious start, strong finish

The KOSPI opened strong at 6,438.50 (+1.47%), dipped to 6,413.50 (+1.07%) in early trade, then picked up steam as the session progressed. It hit a high of 6,668.43 (+5.09%) in the afternoon before pulling back, then surging again to close at 6,579.04 (+3.68%). The rally accelerated so quickly at one point it even triggered buy-side circuit breakers.

Looking at flows: foreigners bought net ₩2.84 trillion, institutions bought ₩527.6 billion. Retail sold ₩3.19 trillion net. Foreigners have been buying for two straight sessions, institutions for four straight—retail has been selling for two consecutive days. The fact that retail dumped over ₩3 trillion on a day the index surged 3%+ shows this rally was driven by foreigners and institutions, not retail. The KOSDAQ told the opposite story: retail bought ₩314.9 billion there, while foreigners and institutions sold ₩160.7 billion and ₩147.7 billion respectively, leaving the KOSDAQ up just 0.12% at 858.91.

Compiled and sourced directly

Why did foreigners pile into semiconductors today? — The Temasek story

The catalyst for today's surge is Singapore's sovereign wealth fund, Temasek. Word is Temasek, one of Asia's largest sovereign wealth funds, has decided to invest directly in Samsung Electronics and SK Hynix and is coordinating with the Korean government on timing. What caught the market's attention: Temasek is handling this with in-house staff rather than external managers, and this is Temasek's first Korean equity market investment ever. Temasek sees memory semiconductors as the most undervalued part of the AI value chain and plans to grow its AI-related investment allocation from 6% to as much as 15% of total portfolio assets over the next five years.

Add to that reports Samsung and SK Hynix could return as much as ₩300 trillion combined to shareholders given their record profits from the semiconductor boom, and overnight in the US, AI cloud company CoreWeave and server maker Super Micro Computer both beat expectations on earnings and guidance, reconfirming the AI infrastructure investment boom. With all three catalysts hitting at once, Samsung Electronics shot up 6.68% and SK Hynix 5.54%, lifting the KOSPI by over 4 percentage points with just those two stocks.

Samsung Electronics 3-month daily chart (Naver Finance, red=up/blue=down)

SK Hynix 3-month daily chart (Naver Finance, red=up/blue=down)

What else jumped — construction and cosmetics rose for totally different reasons

The other two strong sectors, construction and cosmetics, rallied for completely different reasons. Construction stocks surged on hopes for earlier groundbreaking on a second semiconductor cluster in the Honam region: Geumho Engineering hit the daily limit up for the second straight day (+29.94%), while Namhwa Construction (+29.93%) and Koolon Global (+13.51%) also jumped sharply. The bet is that expanded semiconductor capex flows into construction orders—same roots, different branch.

Stock	Move	Reason
Korean Kolmar	+22.80%	Q2 earnings surprise
Cosmax	+18.81%	Record Q2 profit
Iljin Electric	+17.31%	Power equipment, record Q2 profit
Doosan Tesna	+15.14%	Semiconductor test play, buyback hopes

Cosmetics, on the other hand, rose on fundamentals alone. Korean Kolmar (+22.80%) and Cosmax (+18.81%) delivered Q2 earnings surprises, and with forecasts that Korean cosmetics could top the world in exports next year, beauty stocks surged across the board. Organic Timeoscosmetics (+29.80%) and Silicone Two (+12.98%) led the charge.

Semiconductors up 6%, but why did Celltrion drop 4%?

Not everything rose with the KOSPI's 3.68% jump. Pharma and biotech actually fell: Celltrion (−4.04%), Samsung Biologics (−3.73%). The culprit? Tonight's US CPI print. The market expects July's headline CPI to have risen 0.1% month-on-month and core CPI 0.2%, but if either comes in hotter than expected, rate-cut hopes evaporate. Rate-sensitive biotech and pharma stocks priced in this wariness, moving against the index. Semiconductors rose on idiosyncratic catalysts (Temasek, buybacks, earnings) independent of CPI, while biotech got caught by macro headwinds. The same played out on KOSDAQ, where Alteo Genetics (−3.05%) and L&C Bio (−10.55%) tanked along with the rest of biotech.

Celltrion 3-month daily chart (Naver Finance, red=up/blue=down)

Korean Kolmar 3-month daily chart (Naver Finance, red=up/blue=down)

Why didn't KOSDAQ jump as much — new listings and earnings misses weighed it down

The KOSDAQ barely budged, up 0.12% to 858.91. While semiconductors (Juseong Engineering +7.14%, TC Kem +14.21%, Doosan Tesna +15.14%) and cosmetics (Organic Timeoscosmetics +29.80%) showed strength, debuts tanked: Delicious plunged 26.57% on its first day, and Pearl Abyss sank 14.50% after Q2 missed consensus, capping the index. The divergence among large-cap KOSDAQ names kept the index from matching KOSPI's surge.

Is this move real—or just one day's story? What to watch

The two pillars of today's rally—Temasek's rumored investment and CoreWeave/Super Micro's upside—are both still in 'expectation' phase. Temasek hasn't officially announced the timing or size of its actual investment, and the ₩300 trillion shareholder return forecast for Samsung and SK Hynix is market chatter, not official guidance. The fact that retail has dumped over ₩3 trillion two days running suggests retail investors aren't quite buying the rally yet. If tonight's US CPI comes in hotter than expected, the index could shake again after today's semiconductor-powered surge, so the number bears close watching.

You can find more detail on the Honam semiconductor cluster theme driving construction stocks in my post on how Geumho Engineering hit the daily limit, and the divergence between semiconductor exports and shipbuilding/defense in yesterday's post on the KOSPI bounce.

What do bonds and the won tell us about today's rally?

The stock market's 3%+ surge didn't fully convert the bond market to risk-on. 3-year government bond yields fell 1.7bp to 3.791%, and 10-year yields fell 0.7bp to 4.294%. 3-year bond futures rose 6 ticks on financial company and bank buying, 10-year futures 5 ticks. Stocks soaring while bond yields fall suggests bond traders still see this as a semiconductor-specific, catalysts-driven rally rather than a broadening economic improvement. The dollar-won rate at 3:30 p.m. was 1,415.7, up 2.7 won from the prior session's close—no strong won strength alongside the rally. When stocks, bonds, and FX send different signals, it's a sign today's move is built on 'expectations' not 'confirmation.'

KOSDAQ daily chart (Naver Finance)

Investment decisions and outcomes are yours to own.

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