The Nikkei Stock Average fell for a second straight session on the Tokyo Stock Exchange, dropping ¥518.35, or 0.81%, to ¥63,492.99 on the 14th. Investor sentiment weakened as concerns over the pace of U.S. artificial intelligence development combined with higher crude oil prices linked to escalating Middle East tensions. Selling concentrated in heavily weighted AI and semiconductor shares after a report said U.S.-based OpenAI had decided against an initial public offering this year. SoftBank Group, an investor in OpenAI, fell more than 10% at one point, while Advantest and other semiconductor-related stocks also declined. The Nikkei briefly plunged ¥1,285, or 2.01%, to ¥62,726.18, breaking below the psychologically important 64,000 level, before bargain-hunting narrowed the loss. TOPIX (Tokyo's broader stock index) rose 29.91 points, or 0.74%, to 4,058.21, reflecting buying in stocks that had previously fallen. About 77% of Prime Market listings advanced, and trading value reached ¥3.9148 trillion, approximately $25.4 billion. Kentaro Shida, head of research at Yamawa Securities, said renewed reports that OpenAI had shelved a year-end IPO accelerated selling in AI and semiconductor names. He said the absence of earnings-related catalysts could keep semiconductor stocks top-heavy until the next earnings season. Rising U.S. crude futures amid intensifying attacks in the Strait of Hormuz also raised concerns about pressure on corporate earnings and consumer spending. Market participants are focused on upcoming earnings from U.S. semiconductor companies and indicators of AI-related capital spending for the next direction of the market.