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The AI trade just got a reality check, and it echoed across the Pacific. Japanese and South Korean semiconductor stocks cratered on June 23 after US technology shares dropped sharply, dragging Asia’s most important chip companies into a broad, painful correction.
SK Hynix and Samsung Electronics each fell more than 12% on the day. Japan’s SoftBank plunged 15%. The Kospi index in South Korea dropped as much as 10%, triggering two trading halts over the course of the week. Japan’s Nikkei 225 slid roughly 3.6%.
What happened in the US that caused this
The selloff started where most semiconductor selloffs start these days: Nvidia’s neighborhood. A measure of US chip stocks dropped 6.3% on the day that kicked off the rout, with Micron Technology falling 13%.
Semiconductor stocks had been riding a historic rally fueled by AI demand for memory and logic chips. Record highs were hit earlier in 2026. Then profit-taking set in across Nasdaq-listed chip names, and the question shifted from “how high can this go” to “wait, is this overheated.”
Asia’s response was violent
South Korea’s trading environment turned genuinely chaotic. The Kospi experienced daily swings of 8-10% on certain days in early June, the kind of volatility that triggers circuit breakers and makes risk managers lose sleep.
The concentration problem is real. South Korea’s stock market is heavily weighted toward a handful of semiconductor giants, meaning that when Samsung and SK Hynix stumble, the entire index goes with them.
Japan wasn’t spared either. Tokyo Electron and Advantest, two critical suppliers in the global chip equipment food chain, saw significant declines. SoftBank’s 15% plunge added extra weight to the Nikkei’s losses.
The AI valuation question
Micron’s 13% single-day decline tells that story clearly. The company makes memory chips that are essential for AI training and inference workloads. Its fundamentals haven’t deteriorated overnight. But its stock price had climbed to levels that assumed near-perfect execution and uninterrupted demand growth.
The same dynamic applies to SK Hynix, which supplies high-bandwidth memory chips to Nvidia and other AI hardware makers.
What this means for investors
The selloff exposes a structural vulnerability in Asian equity markets. When a handful of semiconductor companies represent an outsized share of an entire national index, corrections don’t stay contained. They become systemic events, complete with trading halts and circuit breakers.
The Kospi’s 10% single-day plunge wasn’t caused by a recession, a geopolitical crisis, or a supply chain disruption. It was caused by a valuation reset in a sector that had gotten ahead of itself.
Disclosure: This article was edited by Editorial Team. For more information on how we create and review content, see our Editorial Policy.
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