Japan Stock of the Day | Kabutaro & Friends

On September 4, 2026, the most talked-about Japanese stock online was SoftBank Group <9984>.
Background: Buying was driven by news that OpenAI had begun providing its new AI model "GPT-6 Astra" to a limited group of companies, seen as the first major update to its foundation technology since August 2025. More than 70% of SoftBank Group's holdings are accounted for by OpenAI and Britain's Arm Holdings, and a rise in Arm shares, together with gains in U.S. technology stocks as expectations for an early rate hike receded, added to investor confidence. The stock widened its gains from an opening price of 5,197 yen, reached a high of 5,611 yen and closed at 5,590 yen, up 589 yen (+11.78%), a fourth straight advance. Trading volume swelled to 77.8 million shares and turnover to 423 billion yen, with a market capitalization of 31.93 trillion yen. The stock alone lifted the Nikkei Stock Average by 461 points, and the index rebounded for the first time in five sessions.