Asian markets delivered one of their most explosive sessions in recent memory on Thursday, May 21, 2026. The KOSPI surged 8.42% — its largest single-day gain in years — as two simultaneous catalysts hit overnight: Nvidia’s blowout Q1 FY2026 earnings and the suspension of the Samsung Electronics workers’ strike. Japan, Taiwan, and other semiconductor-linked markets followed sharply higher. China and Hong Kong diverged, with both falling more than 1%, reflecting the AI rally’s uneven reach across Asia (Reuters via Investing.com).
South Korea: KOSPI +8.42% — A Historic Single-Day Move
The KOSPI closed at 7,815.59, up 606.64 points (+8.42%) from the prior session’s 7,208.95. The index hit a high of 7,819.23 before paring gains into the close. The KOSDAQ rose 4.73% to 1,105.97, led by smaller-cap semiconductor and AI-related names.
Why Korea Moved This Much
1. Nvidia Q1 FY2026 Earnings Beat. Nvidia reported results decisively above consensus after the U.S. close on May 20. As the world’s primary supplier of AI training GPUs, Nvidia’s demand signal translates directly into orders for Samsung Electronics (DRAM, HBM memory) and SK Hynix (HBM3E). Korea is the most concentrated national market on Nvidia’s supply chain, which explains the outsized index move relative to other Asian markets.
2. Samsung Electronics Strike Suspended. The Samsung Electronics workers’ union suspended its strike on May 21, removing a key production uncertainty for the world’s largest memory chip maker. The news directly improved the near-term earnings outlook for Samsung, which is the largest KOSPI constituent by market cap (Reuters via Investing.com).
3. Iran Peace Deal — Lower Oil. WTI crude fell further on May 21 to $96.35/bbl (−1.94%), extending the prior session’s 8.82% collapse. As a major oil-importing economy, Korea benefits directly from lower energy prices through reduced input costs, improved current account dynamics, and eased inflation expectations. The combination of a weak oil price and a strong Nvidia result created an unusually clean macro backdrop for Korean equities.
Japan: Nikkei +3.14% — AI Hardware Names Lead
The Nikkei 225 closed at 61,684.14, up 1,879.73 points (+3.14%), after opening at 60,374.84. Japan’s AI-related hardware ecosystem — including semiconductor equipment makers such as Tokyo Electron and Advantest — rallied sharply as Nvidia’s strong guidance implied continued capital expenditure in AI infrastructure. The USD/JPY exchange rate was essentially flat at 159.03 on May 21, providing no currency headwind for Japan’s export-oriented names.
Japan’s Nikkei had softened in the days prior (−1.23% on May 20, −0.44% on May 19), making the index somewhat oversold relative to the underlying earnings environment. The Nvidia result provided the catalyst to close that gap rapidly.
Taiwan: TAIEX +3.37% — TSMC and the Nvidia Chain
The Taiwan Weighted Index (TAIEX) gained 3.37% to 41,368.21, with an intraday high of 41,606.91. The direct beneficiary of Nvidia’s results in Taiwan is TSMC, the world’s largest contract chip foundry and the primary manufacturer of Nvidia’s GPU dies. A strong Nvidia earnings beat with positive revenue guidance is a direct revenue signal for TSMC, which carries the largest weighting in the TAIEX. The 3.37% index gain understates the individual move in TSMC-adjacent names on the day.
China and Hong Kong: Divergence Widens
The Hang Seng fell 1.03% to 25,386.52, reversing a gap-up open (25,833.24). The Shanghai Composite dropped 2.04% to 4,077.28, also opening higher before selling off decisively.
The divergence from the rest of Asia reflects a structural disconnect: the Nvidia earnings cycle does not translate directly into Chinese AI equity gains under the current U.S. export control framework. Advanced Nvidia GPUs (H100, H200) are restricted from export to China. Chinese domestic AI chip developers (e.g., Cambricon, Biren) are not comparable beneficiaries of the same demand shock. The opening gap-up in both indexes suggests initial positioning based on the overnight U.S. rally, followed by selling once investors focused on the China-specific disconnect from the Nvidia narrative.
Macro Backdrop on May 21
| Instrument | Close | Change |
|---|---|---|
| KOSPI | 7,815.59 | +8.42% |
| KOSDAQ | 1,105.97 | +4.73% |
| Nikkei 225 | 61,684.14 | +3.14% |
| TAIEX | 41,368.21 | +3.37% |
| Hang Seng | 25,386.52 | −1.03% |
| Shanghai Composite | 4,077.28 | −2.04% |
| WTI Crude | $96.35/bbl | −1.94% |
| US 10Y Yield | 4.584% | +1.4 bps |
| USD/JPY | 159.03 | +0.07% |
Source: Investing.com
What to Watch: The Nvidia Cycle and China’s Divergence
The May 21 session crystallized two structural themes that will dominate Asian equity markets through Q2 2026. First, the Nvidia earnings cycle is the primary driver of cross-border semiconductor capital flows. Any revision to Nvidia’s forward guidance — up or down — will ripple immediately into KOSPI, TAIEX, and Nikkei through the HBM, DRAM, and fab supply chains. Samsung and SK Hynix’s ability to ramp HBM production is now the central execution risk for Korean equities. Second, China’s structural exclusion from the Nvidia AI infrastructure cycle is creating an increasingly pronounced divergence within “Asian tech.” HK and Shanghai investors are not unintelligent — the gap-up and reversal pattern on May 21 shows the market correctly repricing the limited China read-through from Nvidia’s results.
On the macro side, oil at $96 and falling is an unambiguous positive for Korea, Japan, and Taiwan — all net energy importers. Watch for U.S.-Iran ceasefire developments, which remain the swing factor for WTI’s next directional move.
Monitor today’s economic releases and upcoming data from Korea, Japan, and the U.S. on the ECONPLEX Economic Calendar.