Samsung, SK Hynix Sink 7-8% as Yesterday's Buyers Turn Sellers

Samsung Electronics and SK Hynix, the two stocks that led foreign buying just one session earlier, flipped to being the most-sold names on the Kospi on Friday, sinking 7.59% and 8.34% respectively as Middle East tensions sent oil toward $100 and U.S. Treasury yields to their highest level in a year and a half.

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What happened

Samsung Electronics closed down 7.59% at 249,500 won, while SK Hynix fell 8.34% to 1,759,000 won. The selloff dragged the benchmark Kospi index down 5.72% (406.27 points) to 6,690.62, and the Kosdaq dropped 5.32% to 748.22, triggering sell-side sidecar circuit breakers on both exchanges. The won also weakened past 1,475 to the dollar.

The catalyst was macro, not company-specific: an escalating military conflict between the U.S. and Iran stoked fears over Middle Eastern oil supply, pushing crude prices close to $100 a barrel. That inflation scare sent the U.S. 10-year Treasury yield above 4.7% for the first time since January 2025, hammering risk appetite across Asian equity markets. As I covered in Oil Surge Triggers Korea's 21st Sell Sidecar, SK Hynix ADR Slides, this is now the latest in a string of oil-driven sidecar events hitting Korean chipmakers this month.

Why it matters: the flow reversal

What makes Friday's session notable isn't just the size of the drop -- Korean chip stocks have posted similar single-day losses repeatedly this quarter, as detailed in Kospi, Kosdaq Both Trigger Sell Sidecars as Chip Twins Sink 7%. It's who was selling. On the prior trading day, foreign investors were the No. 1 and No. 2 net buyers of SK Hynix and Samsung Electronics. On Friday, they were the No. 1 and No. 2 net sellers of the same two stocks.

• Foreign investors sold roughly 873 billion won of Samsung Electronics and 1.7568 trillion won of SK Hynix.
• Institutions sold roughly 858.8 billion won of Samsung and 867.3 billion won of SK Hynix.
• Across the entire Kospi, foreigners were net sellers of 3.8119 trillion won and institutions net sellers of 1.6574 trillion won.
• Retail investors absorbed nearly all of it, net-buying 5.4403 trillion won of Kospi shares.

That kind of overnight reversal in institutional positioning is a sharper signal than the headline percentage drop -- it suggests the selling was driven by macro risk-off repricing (oil, yields, geopolitics) rather than any change in the underlying fundamentals or earnings outlook for either company.

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Who's affected

The direct hit lands on Samsung Electronics and SK Hynix shareholders, but the ripple extends to SK Hynix's newly listed Nasdaq ADR, which I wrote about in Kospi's 5.7% 'Black Friday' Crash Slams SK Hynix's New Nasdaq ADR -- U.S. investors now have direct dollar-denominated exposure to swings like this one. Retail traders who have been aggressively buying the dip, as they did again Friday with 5.4 trillion won in net purchases, are also increasingly exposed if the macro backdrop doesn't stabilize. More broadly, the same oil-and-yields dynamic that hit Korean chip names has been weighing on U.S. markets too, echoing the pattern from Houthi Attack on Saudi Tankers Sends Oil Past $100, Nasdaq Sinks 2.2%.

What to watch next

Three threads are worth tracking from here:

• Oil and the Middle East conflict. Crude approaching $100 a barrel is the proximate trigger for this entire chain of sell sidecars; any de-escalation or further military escalation will likely move Korean chip stocks and their U.S.-listed peers in tandem.
• The 10-year Treasury yield. A break above 4.7% -- its highest since January 2025 -- raises the cost of capital broadly and pressures growth and tech valuations, including AI-linked semiconductor names.
• Whether foreign selling persists. A single-day flip from top buyer to top seller can be noise, but if foreign and institutional investors keep unwinding positions in Samsung and SK Hynix over the coming sessions, it would point to a more durable repricing rather than a one-off macro shock.

None of this changes the underlying AI memory demand story that has driven both stocks higher for much of the year -- but it's a reminder that even fundamentally strong names remain hostage to oil prices and bond yields when geopolitical risk spikes.

This is not financial advice — always do your own research before making investment decisions.