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On June 23, 2026 the KOSPI plunged 9.99% (910 points) to 8,203.84 after Samsung…

Brief

SurmountInvest recounts the June 23, 2026 KOSPI rout — a 9.99% drop to 8,203.84 after Samsung (-12.3%) and SK Hynix (-12.5%) triggered a circuit breaker — and warns that record retail net buying (11.55 trillion won) funded by a record 38.48 trillion won in margin debt and new 2x ETFs leaves retail overleveraged and at systemic risk.

Why it matters

On June 23, 2026 the KOSPI plunged 9.99% (910 points) to 8,203.84 after Samsung (-12.3%) and SK Hynix (-12.5%) triggered a 20‑minute circuit breaker; the index had closed at an all‑time high of 9,114.55 the previous day after tripling from ~3,000 a year earlier on AI‑chip strength.

Key details

  • Foreign and Korean institutional investors net sold roughly $8.5 billion on June 23 while Korean retail net bought a record 11.55 trillion won (~$7.16 billion); retail margin debt reached a record 38.48 trillion won four days earlier and regulators had approved 2x single‑stock ETFs on Samsung and SK Hynix one month prior.
  • Author's claim: Korean retail now holds the most leveraged position in market history at the highest valuation with "smart money" gone, meaning leverage (margin loans, pledged assets, 2x ETFs) — not the crash itself — is the primary risk; Surmount promotes rules‑based strategies to avoid forced, panic selling.
Source evidence

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South Korea's stock market just had its worst single day in 30 years.

The KOSPI crashed 9.99% in one session.

A 20-minute circuit breaker. $8.5 billion in smart money fleeing.

And retail investors bought every share they were dumping.

Here's what actually happened:

June 23, 2026.

The KOSPI closed Monday at an all-time high of 9,114.55. A year ago it was around 3,000.

The Korean market tripled in 12 months on a single trade. AI chips.

Samsung and SK Hynix together make up roughly half of the entire KOSPI.

Then Tuesday happened.

Samsung dropped 12.3%. SK Hynix dropped 12.5%.

The KOSPI fell 910 points to close at 8,203.84.

Down 9.99%, the fifth largest single day drop since 1996.

Now here's the part the headlines missed.

Foreign investors and Korean institutions combined to net sell roughly $8.5 billion of stock on Tuesday.

On the other side of every sell order was a Korean retail investor.

Retail net bought a record 11.55 trillion won. $7.16 billion in a single day.

The largest day of retail net buying in Korean stock market history.

How were they funding it?

Margin loans.

Four days before the crash, Korean retail margin debt hit an all-time record of 38.48 trillion won.

Investors were taking personal loans, borrowing against insurance policies, and pledging stocks to buy more stocks.

Regulators had also approved 2x leveraged single-stock ETFs on Samsung and SK Hynix one month before the crash.

So retail loaded into 2x products on the two stocks that just fell 12% in a session.

Wednesday the KOSPI bounced. Retail bought even more. Institutions kept selling.

The leverage didn't go anywhere.

Korean retail is now holding the most leveraged position in market history at the highest valuation in market history with the smart money already gone.

That isn't a victory. It is a setup.

The crash itself isn't what wipes retail out. The leverage going into the crash is.

Institutions sell on days like Tuesday because the rules in their system told them to.

Retail runs on conviction, FOMO, and borrowed money chasing a story that "still works."

Being right about AI in 2030 doesn't matter if you get margin called in 2026.

That's what Surmount was built for. Rules-based strategies that hold their size at the top and don't get shaken out at the bottom.

When the next Black Tuesday hits, your system has already decided what to do...

Video

— https://nitter.net/SurmountInvest/status/2070153021372404141#m