SoftBank Group stock surged nearly 13% in Tokyo trading on Monday, extending one of the most closely watched AI rallies in global markets.
The move reflects a deeper re-rating of Masayoshi Son’s sprawling investment group, whose biggest AI bets, including Arm, OpenAI, data centres, and robotics, are now moving in the same direction.
For investors, SoftBank has become one of the cleanest public-market proxies for the artificial intelligence boom.
When confidence in AI infrastructure rises, SoftBank increasingly moves with it.
Arm Holdings: AI chip engine driving SoftBank’s rally
The first reason is Arm Holdings as SoftBank owns nearly 90% of the British chip designer, making every rally in Arm a direct boost to SoftBank’s net asset value.
ARM does not manufacture chips. But its architecture sits at the heart of processors used across smartphones, servers, and, increasingly, AI-linked computing systems.
That makes it a key beneficiary of the infrastructure spending wave triggered by demand for generative AI.
UBP senior equity adviser Vey Sern Ling told CNBC that “SoftBank’s share price is simply reflecting the moves of its stake holdings, including Arm, whose share price has been surging.”
OpenAI jackpot: $45 billion paper gain
The second driver is OpenAI. SoftBank has committed to invest heavily in the ChatGPT maker, with its cumulative investment expected to reach $64.6 billion after planned follow-on tranches.
That bet is already showing up in SoftBank’s accounts as the company has booked about $45 billion in gains linked to its OpenAI investments.
OpenAI’s confidential filing for a US IPO on June 8 has only sharpened investor attention.
Rolf Bulk of Futurum Group, quoted by TIKR, described SoftBank as offering “early exposure to the OpenAI IPO” and access to “the fastest growing segment in AI semis.”
Earnings blowout: When a profit surge forces attention
SoftBank’s rally also has a straightforward earnings story behind it.
The company reported a record annual profit of about 5 trillion yen for the year ended March 2026, helped by gains from OpenAI and other AI-linked holdings.
Revenue rose to roughly 7.8 trillion yen, while the Vision Fund booked a major OpenAI-driven gain in the March quarter.
The result also helped shift analyst sentiment. SMBC Nikko raised its SoftBank price target to 8,500 yen from 5,200 yen, citing improved exposure to Arm.
Son’s grand vision
The rally has restored Masayoshi Son’s image as one of the market’s great risk-takers.
On June 1, SoftBank briefly overtook Toyota as Japan’s most valuable listed company, a symbolic moment for both the group and the country’s equity market.
Son is also pushing beyond financial exposure.
SoftBank has pledged tens of billions of euros for AI infrastructure in France and remains a central backer of Stargate, the $500 billion US AI infrastructure project involving OpenAI and Oracle.
In a CNBC interview, Son said the AI revolution could be far larger than the dot-com boom and argued that physical AI and robotics could become the next trillion-dollar opportunity.
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