日韓股市「黑色星期二」：韓股熔斷，日經重挫，AI熱潮迎來階段性調整

Original | Odaily Planet Daily (@OdailyChina)

Author | Qin Xiaofeng (@QinXiaofeng 888 )

Today, Asian stock markets experienced severe turbulence.

The Korea Composite Stock Price Index (KOSPI) plummeted over 8% intraday, triggering the market's circuit breaker mechanism and suspending trading for 20 minutes; it eventually closed nearly 10% lower at 8203.84 points, marking the third-largest single-day drop this year. Japan's stock market also came under pressure, with the Nikkei 225 falling about 3.5% to close near 69,788 points, ending eight consecutive days of gains. The TOPIX index fell approximately 2.6%.

This correction hit tech stocks, especially the semiconductor sector, the hardest. Heavyweights like Samsung Electronics and SK Hynix were leading decliners, dragging down the entire market. Foreign investors accelerated selling, trading volumes surged sharply, and panic sentiment in the market noticeably escalated.

Since June, stock markets in Japan and South Korea have experienced multiple instances of sharp volatility. The KOSPI has triggered circuit breakers four times this year. Previously driven by the AI and semiconductor boom, the KOSPI approached an all-time high of 9,385 points, and the Nikkei 225 briefly stood above 70,000 points. In just a few weeks, the shift from record highs to a significant correction highlights market fragility and profit-taking pressure. Odaily Planet Daily analyzes this from three perspectives: market performance, underlying causes, and future trends.

1. Market Plunge: From Historic Highs to Circuit Breaker Alarms

Opening on June 23, the KOSPI started higher at 9083.54 points, briefly surging to 9175.45 points intraday. However, propelled by foreign selling and panic-driven selling, the index rapidly plummeted. Around 14:33 p.m., the decline exceeded 8%, triggering the Korea Exchange (KRX) circuit breaker, halting trading in all KOSPI stocks for 20 minutes. This mechanism was previously activated on June 5th and 8th, among other days, indicating that volatility has become the norm.

At the close, the KOSPI stood at 8203.84 points, a single-day drop of 9.99%, with trading volume surging to 48.371 billion shares. Semiconductor giants SK Hynix and Samsung Electronics were among the worst hit, each falling over 12%. The KOSDAQ index, more vulnerable, also plummeted over 6%, with small-cap tech stocks falling broadly. Net selling by foreign investors was significant, becoming the main source of selling pressure.

The Japanese market's reaction was relatively milder but still noteworthy. The Nikkei 225 fell over 3% intraday, closing around 69,788 points for a single-day drop of approximately 3.47%, while the TOPIX index also declined. Tech and semiconductor-related stocks performed the worst: SoftBank Group fell over 10%, chipmaker Kioxia plunged 15.1%, and Tokyo Electron dropped 6.2%. The AI and semiconductor sectors that previously drove the Nikkei's rally experienced a broad correction, ending a streak of eight consecutive trading days of gains.

Compared to recent highs, the magnitude of this correction is astonishing. The KOSPI has fallen over 12% from its mid-June peak, and the Nikkei 225 has seen a significant pullback from above the 70,000-point level.

The global market linkage is evident. U.S. tech stocks came under collective pressure overnight, with the Nasdaq falling over 1% and the S&P 500 edging lower. The "Magnificent Seven" saw rotation, with stocks like Amazon and Meta leading the decline. Other Asian markets, such as Taiwan, were also affected, forming a regional tech stock sell-off wave.

Overall, this is a rapid and severe correction led by the tech sector, with the South Korean market, due to its high concentration, experiencing a much larger drop than Japan.

2. Cause Analysis: A Phase Rupture of the AI Bubble Under Multiple Factors

The sharp decline in Japanese and South Korean stocks results from a combination of factors, which can be analyzed from direct triggers, macro-policy pressures, and structural risks.

1. Direct Triggers: Weak Overnight US Tech Stocks and Profit-Taking Pressure

The significant correction in the US tech sector on the previous trading day directly transmitted to Asian markets. The Nasdaq fell over 1.2%, with significant rotation within the "Magnificent Seven" and noticeable pressure on some individual stocks.

Lisa Shalett, Chief Investment Officer (CIO) at Morgan Stanley Wealth Management, pointed out: "There is clear rotation within the Magnificent Seven. News of departures by some executives or researchers has exacerbated market concerns about the pace of AI commercialization. Investors are beginning to demand more evidence that massive AI capital expenditures can translate into sustainable profitability."

This concern quickly impacted the Japanese and South Korean markets, which are highly dependent on the global AI supply chain. South Korea's semiconductor exports consistently account for over 20% of its total exports, and Samsung Electronics and SK Hynix together represent approximately 40% of the KOSPI's weight. On June 23, the two giants fell approximately 8%-12%, directly dragging down the index.

Furthermore, Japanese and South Korean stock markets had accumulated significant gains since June, creating substantial unrealized profits. The KOSPI surged from around 5,000 points at the start of the year to above 9,000 points by mid-June, a year-to-date gain of over 80%. The Nikkei 225 also rose from about 40,000 points to above 70,000 points, hitting record highs. With valuations at elevated levels (the KOSPI's forward P/E ratio briefly approached historical highs), any negative catalyst could easily trigger profit-taking. The concentrated selling on June 23 was a natural correction following an excessively rapid prior advance.

2. Macro and Policy Factors: Rising Fed Rate Hike Expectations and Economic Data Impact

Strong recent US employment data has further fueled market expectations that the Federal Reserve will maintain high interest rates or even hike them. According to Reuters, non-farm payrolls increased by 172,000 in May, far exceeding economists' forecast of 85,000, while the unemployment rate stabilized at 4.3%. This data prompted some institutions (like Goldman Sachs) to push back their first rate cut expectation to 2027. More critically, the Fed's FOMC meeting on June 16-17 decided to keep the federal funds rate target range unchanged at 3.5%-3.75%. The meeting statement emphasized that economic activity is expanding at a solid pace, but uncertainty due to the Middle East conflict has increased, and inflation remains above the 2% target.

The Fed's latest dot plot sent a clear hawkish signal: the median federal funds rate forecast for end-2026 was raised to 3.8% (significantly up 0.4 percentage points from the 3.4% forecast in March), suggesting at least one rate hike within the year. Simultaneously, the FOMC raised its inflation forecasts for 2026: the median core PCE inflation forecast rose to 3.3%, and headline PCE to 3.6% (both previously around 2.7%); the GDP growth forecast was slightly lowered to 2.2%.

Consequently, growth stocks sensitive to interest rates, particularly the tech and semiconductor sectors, bore the brunt of the sell-off. Previously treated as typical 'high-beta' assets due to the AI boom, South Korean stocks are extremely sensitive to changes in global liquidity. The Japanese market is similarly constrained by global liquidity expectations, although improved domestic wage growth data provided some support.

The series of macro signals significantly pushed up US Treasury yields, exerting downward pressure on global risk assets and directly intensifying the selling pressure on Japanese and South Korean tech stocks.

3. Structural Risks: High Market Concentration and Foreign Outflows

The structural vulnerability of the South Korean stock market is particularly prominent. The KOSPI's heavy reliance on the two semiconductor giants Samsung Electronics and SK Hynix means the index experiences violent swings whenever the semiconductor cycle or global AI demand fluctuates.

Continued foreign capital outflows are another key factor. Foreign investors achieved substantial gains during the prior rally and have shown net selling multiple times since June, especially in South Korean stocks, with some funds potentially rotating into US IPOs (like SpaceX) or other assets. On June 23, net selling by foreign investors significantly expanded, becoming the main source of selling pressure.

In contrast, while Japan's market was also dragged down by tech stocks, its sector composition is relatively more diversified, limiting the Nikkei 225's decline to around 3.5%.

Additionally, company-specific developments exacerbated market pressure. According to market sources, SK Hynix recently adjusted its AI chip (especially HBM) memory capacity allocation, shifting some production lines towards more profitable traditional DRAM to optimize near-term profitability. This move raised investor concerns about the short-term supply-demand balance of HBM, triggering selling.

Therefore, the massive sell-off on June 23 was not an isolated event but the result of the premature pricing of AI expectations failing to meet short-term performance proofs, combined with a shift in global liquidity expectations and accumulated profits from a rapid early rally.

3. Future Outlook: Short-Term Volatility Inevitable, Long-Term AI Narrative Remains Resilient

Looking ahead, Japanese and South Korean stock markets will likely exhibit characteristics of 'volatile consolidation and structural divergence'. Short-term market volatility will remain high, but medium-to-long-term fundamental support persists, and the correction offers a window for positioning in quality assets.

Short-term volatility prevails; recovery depends on US stocks and Fed signals. In the near term, the market remains in a high-volatility adjustment phase. The performance of US tech stocks is a key barometer. If the Nasdaq stabilizes or sees a technical rebound, Japanese and South Korean markets may follow suit. Conversely, if the Fed releases further hawkish signals or Q2 corporate earnings in Japan and South Korea disappoint, the correction could persist or deepen. Key events to watch include:

• US inflation (CPI/PCE) and employment data for June-July;
• The Fed's next FOMC meeting (July);
• Q2 earnings reports from heavyweight stocks like Samsung Electronics, SK Hynix, and Tokyo Electron.

Medium-to-long-term fundamentals remain robust; corrections present opportunities. Global AI capital expenditure continues to grow at a high rate, and the underlying logic of the semiconductor super-cycle remains unchanged. According to forecasts from Goldman Sachs and other institutions, cumulative global AI-related capital expenditure (computing, data centers, power) from 2026-2031 will total approximately $7.6 trillion. AI CapEx alone in 2026 is close to $765 billion, rising annually to $1.6 trillion by 2031. New data center capacity additions are expected to total nearly 100GW from 2026 to 2030, with total investment reaching the $3 trillion level.

South Korea holds a strong leading position in HBM and advanced manufacturing processes. SK Hynix's HBM market share has consistently remained between 50%-62%, and its supply share for the NVIDIA Rubin platform in the HBM4 era could reach around 70%. Samsung Electronics is also accelerating capacity expansion, planning to increase HBM production capacity by approximately 50% in 2026. Long-term orders for both giants are largely secured through 2027, and the AI memory demand super-cycle is still in its early stages.

From a long-term perspective, AI remains a productivity tool capable of reshaping the world order. Periodic adjustments struggle to reverse the overarching trend of technological progress. As with corrections following every technological bubble in the past, they ultimately left substantial rewards for true infrastructure builders and innovators. This 'Black Tuesday' may mark a turning point where AI investment transitions from frenzy to rationality and from concept to industry. The resilience and potential of Japanese and South Korean stock markets remain worthy of anticipation.