Japan’s benchmark Nikkei 225 index blew past 67,000 for the first time on June 1, closing the midday session at 67,038.24 after touching an intraday high of 67,231.28. The catalyst was not a broad-based rally. It was overwhelmingly one stock: SoftBank Group.
SoftBank shares surged 10.3% in a single session, contributing 618 of the index’s total 709-point gain. That means one company was responsible for roughly 87% of the Nikkei’s move.
SoftBank reclaims Japan’s throne
The rally pushed SoftBank’s market capitalization beyond ¥46 trillion, or roughly $288 billion. That figure nudged it past Toyota, which sat at ¥45.8 trillion, making SoftBank Japan’s most valuable publicly traded company for the first time since 2000.
SoftBank’s stock has gained more than 80% year-to-date. Toyota, meanwhile, has declined by over 10% during the same period.
The OpenAI bet and beyond
SoftBank has invested more than $30 billion in OpenAI through its Vision Fund 2, with follow-on investments continuing throughout 2026. That stake reportedly targets around 13% ownership in the maker of ChatGPT.
SoftBank also holds a major position in Arm Holdings, the chip designer whose architecture underpins much of the world’s AI hardware.
SoftBank has committed up to €75 billion ($87 billion) toward European data center development, with an initial tranche of €45 billion directed at France.
What this means for investors
When a single stock can drive nearly 90% of an index’s daily gain, that’s a signal worth paying attention to. SoftBank’s investments span the full stack, from chips (Arm) to applications (OpenAI) to physical infrastructure (data centers).
SoftBank’s previous adventures in concentrated bets, most notably the original Vision Fund’s exposure to WeWork and other high-profile stumbles, should remind investors that Masayoshi Son’s conviction trades can cut both ways.
At $288 billion, SoftBank’s market cap now exceeds many standalone AI companies. Investors buying at these levels are effectively betting that OpenAI’s trajectory, Arm’s dominance in AI chips, and the data center buildout will all continue to deliver.