Japanese and South Korean Stocks Plunge as Sell-Off Intensifies, KOSPI Triggers Circuit Breaker

October 15, 2026

Japanese and South Korean stock markets suffered sharp losses on Thursday as a renewed wave of selling swept across Asian equities, intensifying concerns over global technology valuations and the outlook for interest rates. South Korea’s benchmark KOSPI index plunged about 8% and triggered a market-wide circuit breaker, while Japan’s Nikkei 225 fell as much as approximately 5% during the session.

The sell-off was driven by hotter-than-expected U.S. inflation data, shifting expectations for Federal Reserve policy and renewed pressure on artificial intelligence and semiconductor-related stocks.

South Korea’s KOSPI Plunges, Triggering a Trading Halt

South Korean shares came under heavy pressure from the opening bell on October 15. Selling accelerated throughout the session, pushing the KOSPI down approximately 8% and triggering a 20-minute trading halt under the exchange’s circuit-breaker mechanism.

The index eventually closed at 5,528.05, its lowest closing level since late July, extending its losing streak to seven consecutive sessions.

Major technology stocks led the decline. Samsung Electronics fell approximately 9.7%, while SK Hynix dropped more than 11%. Other large companies, including LG Energy Solution and Hyundai Motor, also recorded significant losses.

Foreign investors added to the pressure by selling a net 2.9 trillion won worth of South Korean shares, according to market data. The combination of heavy institutional selling and declining technology stocks left the benchmark particularly vulnerable.

Japanese Equities Also Slide as Technology Stocks Weaken

Japan’s stock market experienced a parallel downturn. The Nikkei 225 fell sharply, with its intraday decline reaching approximately 5%. SoftBank Group, Kioxia Holdings and Tokyo Electron were among the technology-related companies facing significant selling pressure.

The weakness followed losses in U.S. technology stocks, as investors reassessed valuations across the artificial intelligence industry and questioned whether expected future returns would justify the sector’s substantial investment requirements.

Although Japan and South Korea have different economic structures and market dynamics, both have significant exposure to technology exports and the global semiconductor supply chain. This leaves their equity markets vulnerable when investors reduce exposure to high-growth technology companies.

Hot U.S. Inflation Data Raises Concerns Over Interest Rates

A key catalyst for Thursday’s market turmoil was the latest U.S. inflation report. The Consumer Price Index rose 3.7% year over year in September, exceeding market expectations and prompting investors to reassess the Federal Reserve’s policy outlook.

Expectations for higher interest rates can increase corporate borrowing costs and reduce the present value of future earnings, placing pressure on highly valued growth stocks. Investors have become particularly sensitive to financing costs, debt burdens and returns on investment in capital-intensive sectors such as AI infrastructure, data centers and semiconductors.

As U.S. technology shares weakened, selling spread across Asia’s semiconductor supply chain. Investors moved to reduce risk exposure, amplifying declines in both Japanese and South Korean equities.

Market Recovery Depends on Inflation, Earnings and Investor Confidence

The sharp declines do not necessarily mean that Japanese and South Korean markets have entered a prolonged bear market, but near-term risks have increased considerably.

Investors will closely monitor upcoming U.S. inflation and employment data, Federal Reserve commentary, movements in the dollar and bond yields, and earnings reports from major technology companies.

If inflation remains elevated and interest-rate expectations rise further, technology stocks and export-oriented companies could face additional valuation pressure. Conversely, more stable rate expectations and renewed investment demand could help markets recover some of their losses.

For now, continued volatility remains a significant risk. Investors should be cautious about assuming that a short-term rebound signals a lasting recovery, particularly when selling pressure, liquidity conditions and leveraged positions remain key factors in market movements.