South Korean and Japanese stocks led a sharp Asian technology sell-off on Tuesday as investors reassessed the profitability of the region’s biggest AI winners.
The KOSPI fell as much as 7.4% to 5,914.35, its lowest since late July, while the Nikkei 225 dropped about 2.5% to around 67,300 as Tokyo reopened after Monday’s Sports Day holiday.
The declines followed another weak US semiconductor session and fresh concern that China’s ChangXin Memory Technologies, or CXMT, is narrowing the technology gap in advanced memory.
The damage was concentrated in chips, but high oil prices and still-elevated bond yields made the valuation reset harder to ignore.
Why the KOSPI is taking the biggest hit
Korea is where the competitive threat lands most directly. Samsung Electronics fell about 8.7% and SK Hynix dropped roughly 9.2%, dragging the benchmark sharply lower.
The Korea Exchange triggered a five-minute sell-side sidecar after KOSPI 200 futures fell more than 5%.
CXMT said it had made progress on a 4F² memory-cell architecture that can increase density by fitting more cells on a chip.
The company plans to introduce server memory using the structure by year-end, according to the South China Morning Post.
That does not mean CXMT is already taking large-scale high-end market share from Samsung or SK Hynix.
The immediate concern is future pricing power. If Chinese supply becomes more competitive, the scarcity premium supporting today’s exceptional memory margins could shrink.
SLC Management strategist Dec Mullarkey told the Financial Times that investors remain wary because chipmakers have a long history of painful boom-bust cycles, making unusually large profits difficult to treat as permanent.
Why the Nikkei 225 is falling for a different reason
Japan’s decline is broader than a pure memory-competition trade. SoftBank Group, Kioxia and Advantest all came under pressure as Tokyo caught up with the global chip sell-off after Monday’s holiday.
SoftBank stock was down more than 8%, Kioxia about 8.8% and Advantest roughly 7% during the session.
That matters because technology accounts for about 45% of the Nikkei, leaving the benchmark unusually sensitive when investors question both semiconductor profits and the returns available from huge AI investment programmes.
Commerzbank analysts told the Wall Street Journal that energy-driven risk and technology weakness were the main forces weighing on markets.
MUFG strategist Michael Wan added that weakness in US semiconductor shares was spilling directly into Asian equities.
Why this is bigger than one bad chip session
The rest of Asia also weakened, but Korea remained the clear outlier. Taiwan’s Taiex fell about 2.5%, with TSMC down roughly 2%, while Hong Kong’s Hang Seng and the Shanghai Composite lost around 1%.
The macro backdrop is adding another layer of pressure. Brent traded around $105 a barrel while the US 10-year Treasury yield hovered near 5.2%, keeping both inflation and discount-rate risks elevated.
That combination makes Tuesday’s sell-off more important than another volatile AI session. Demand for AI computing has not suddenly collapsed.
Investors are instead questioning who keeps the extraordinary profits if Chinese memory competition rises just as expensive capital makes premium valuations harder to defend.
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