After the US stock market experienced "Black Friday", the South Korean stock market fell to trigger the circuit breaker.

On June 8, the decline of South Korea's KOSPI index at the opening widened to over 8%. Both Samsung Electronics and SK Hynix fell nearly 10%, triggering the first - level circuit - breaker mechanism, and trading was suspended for 20 minutes. Subsequently, after the circuit - breaker mechanism was lifted, the KOSPI index resumed trading, and the decline narrowed slightly. The Nikkei 225 index also opened significantly lower, with a decline of more than 4%.

In the Chinese market, the Shanghai Composite Index opened down more than 2%, falling below the 4000 - point mark. The Shenzhen Component Index and the ChiNext Index fell more than 3%, and the STAR Market Composite Index fell more than 4%. Then they gradually rebounded. The Hong Kong stock market also opened lower, with the Hang Seng Index and the Hang Seng Tech Index falling nearly 2%.

Just before the opening, the Korea Exchange urgently held a market assessment meeting to evaluate the current volatility situation and discuss countermeasures to stabilize the market operation. The meeting focused on reviewing the sharp decline in the U.S. stock market and the overnight futures market trends, and discussed corresponding market management plans. The Korea Exchange said that it will strengthen the emergency response mechanism of all institutions, closely monitor global market dynamics, the evolution of the Middle East situation, and foreign exchange market trends. At the same time, it will increase the supervision of unfair trading behaviors and expand the scope of inspections of illegal short - selling activities.

Recently, the volatility of the South Korean stock market has intensified, and trading suspensions have occurred frequently. Two weeks ago, on May 27, the KOSPI triggered a programmatic trading suspension due to a 5% increase at the opening. On May 15, after the KOSPI reached 8000 points, it suddenly reversed, also triggering a programmatic trading suspension.

The repeated switching between sharp rises and falls exposes the structural vulnerability of the South Korean stock market, which is highly concentrated in two semiconductor companies. Since the beginning of this year, Samsung Electronics and SK Hynix have contributed more than half of the KOSPI's gains, and the two companies also account for more than half of the KOSPI index weight. The extremely high concentration makes any minor changes in the semiconductor industry be magnified exponentially.

The direct external cause of this panic is the "Black Friday" in the U.S. stock market on June 5. On that day, the S&P 500, the Nasdaq Index, and the Philadelphia Semiconductor Index fell 2.6%, 4.2%, and 10.3% respectively. The Philadelphia Semiconductor Index recorded its largest single - day decline since March 2020. NVIDIA fell more than 6%, Micron Technology fell more than 13%, and Broadcom fell nearly 8%.

Chen Junyun, an analyst at CITIC Securities, pointed out that the adjustment of monetary policy expectations brought about by the strong U.S. non - farm payrolls data in May, combined with the crowded trading in the market before, as well as the upcoming listing of SpaceX, Broadcom's earnings report, and Google's stock issuance for financing, are the main factors for the short - term sharp adjustment of the market. Broadcom's earnings report showed that the demand for its custom AI (artificial intelligence) chip business did not meet the market's high expectations, and it fell a cumulative 19% in two days.

On the eve of the spread of market panic from the United States to Asia, Jensen Huang, the CEO (Chief Executive Officer) of NVIDIA, appeared in Seoul, trying to inject confidence into the market.

On June 7 local time, Jensen Huang had dinner with senior executives such as Choi Tae - won, the chairman of SK Group, and Kwak No - jung, the president of SK Hynix. Jensen Huang said to the media at that time: "Our cooperation covers multiple fields, including artificial intelligence supercomputers, central processing units, new - type personal computers, and robotics technology. This meeting is to finalize relevant plans." He also clearly judged the global shortage of memory chips: "I expect this situation will continue for several years. The entire industry supply chain, from wafers, packaging to silicon - photonics modules, is in short supply, which is rooted in the high - level market demand."

On the morning of June 8, NVIDIA and SK Hynix officially announced a multi - year technology partnership. According to NVIDIA's official announcement, the two sides will conduct joint research and development on the next - generation memory required for the construction of global AI factories and apply AI technology to the design and manufacturing of semiconductor chips. The announcement detailed that SK Hynix will expand into the new markets that NVIDIA is creating, covering three major fields: artificial intelligence infrastructure, personal artificial intelligence, and physical artificial intelligence. The two sides will jointly develop dedicated storage products for NVIDIA's Vera Rubin artificial intelligence supercomputer, Vera central processing unit, personal computers equipped with RTX Spark technology, and Jetson Thor robotic computing platform.

However, multiple positive news failed to stop the sharp decline of the KOSPI at the opening. The deeper structural hidden danger is the radical leveraging of South Korean retail investors. As of mid - May, data from the Korea Financial Investment Association showed that the outstanding balance of margin loans for stock purchases had swelled to 36.47 trillion won, a record high, about twice that of the same period in 2025. The proportion of margin trading has doubled from 18% a year ago to 35%. Lee Chan - jin, the head of the Korea Financial Supervisory Service, has publicly expressed concerns about the risk exposure of retail investors and warned that the trend of funds flowing to high - risk products at an accelerated pace may further intensify market volatility.

Regarding the AI industry, Chen Junyun said: "In the short - term dimension, benefiting from computing power inflation, the bullish logic of the capital market on the AI industry, which is constantly self - reinforcing, is unlikely to reverse. However, the current progress of the AI industry is still significantly far from the argument of 'fully closed - loop commercialization'. The industry still needs to explore more high - value monetization scenarios to match the huge CAPEX investment. The market is expected to continue to maintain a high - volatility state in the short term, and it is extremely necessary to closely monitor the risk of the temporary mismatch between AI investment and output rhythm."

This article is from the WeChat official account "Dushuyizhi" (ID: dushuyizhi007). Author: Cheng Mengqi. Editors: Guo Nan, Lu Ling. It is published by 36Kr with authorization.