The Japanese stock market displayed a significant divergence on Monday, September 14, 2026. The Nikkei 225 index closed 0.81% lower at 63,492.99 points. During the session, the index plummeted by as much as 2% as the selloff in technology shares weighed heavily. In stark contrast, the TOPIX index bucked the trend, rising 0.74% to close at 4,058.21 points.

This pronounced "tech slump, value rebound" divergence is a direct consequence of the "AI safety deceleration storm" that swept through the global AI industry over the weekend.

The catalyst for today's turbulent tech trading originated from across the Pacific. Over the weekend, Anthropic CEO Dario Amodei publicly urged AI enterprises to slow the pace of model capability advancements. This rare industry-wide call for caution triggered a chain reaction on global social media and received unprecedented public endorsements from OpenAI CEO Sam Altman, xAI head Elon Musk, and Google DeepMind Chairman Demis Hassabis. Adding further strain to the capital markets, Altman also clarified that OpenAI has no plans for an initial public offering in 2026 and intends to redirect its full focus toward AI safety. This collective strategic pivot by the global AI leadership directly shattered the market's previous optimistic expectations of rapid, short-term monetization across the AI supply chain.

Where the selloff began

Wataru Akiyama, an equity strategist at Nomura, pointed out that these concerns over AI technology safety cast a heavy shadow over the earnings prospects of global semiconductor and AI infrastructure companies. The decline in Japan's stock market today can almost entirely be attributed to a "targeted, localized financial explosion" in AI and chip-related stocks.

SoftBank Group bore the brunt of the selling as a core venture capital force in OpenAI and the global AI industry. Its shares closed down a brutal 10.72%, marking the largest single-day loss in over two months and making it the biggest drag on the Nikkei average.

Chip and semiconductor hardware stocks were also hit severely. Chip manufacturer Kioxia Holdings Corp tumbled 6.37%, followed closely by semiconductor materials maker Resonac Holdings, which plunged 5.98% during the day. Investors are swiftly reducing their risk exposure to hardware-weighted stocks at the fastest pace possible.