SoftBank Group’s bold investment in OpenAI is paying off as the Japanese technology investor reported a more than doubling of second-quarter net profit to 2.5 trillion yen ($16.6 billion), driven largely by valuation gains in its stake in the ChatGPT-maker.

The results provide SoftBank with additional capital to fund its aggressive artificial intelligence (AI) investment strategy, even as concerns grow over a potential “AI bubble” in which valuations may overstate the profits that AI technologies can deliver.

SoftBank’s earnings announcement on Tuesday coincided with a broader bull run in technology stocks, which has propelled the company’s share price to record highs. In response, SoftBank declared a four-to-one stock split to make its shares more accessible after nearly quadrupling in value over the past six months.

The company has also stepped up fundraising efforts to finance new investments, including selling off equity stakes such as the remainder of its holdings in Nvidia for $5.83 billion, issuing bonds in multiple currencies, and taking out bridging loans. SoftBank has repeatedly invested in Nvidia, selling its stake before the AI boom, then repurchasing shares prior to October’s divestment to focus on OpenAI.

When asked about the timing of the Nvidia sale, Chief Financial Officer Yoshimitsu Goto declined to comment directly but explained that SoftBank needed to leverage existing assets to fund its large OpenAI investment. Analysts suggest the move reflects a strategic shift rather than a lack of confidence in the AI sector.

“Son is a savvy investor, so selling the entire stake must mean that he is no longer optimistic about the share price,” said Wong Kok Hoi, founder and CEO of APS Asset Management in Singapore. “Big tech companies may continue to invest heavily in GPU chips but not at this year’s level for many years.”

SoftBank’s AI strategy has been ambitious. In March, it led a funding round of up to $40 billion in OpenAI at a $300 billion valuation. By October, the company was part of a consortium acquiring $6.6 billion worth of shares from OpenAI employees at a higher valuation of $500 billion. SoftBank’s total investment in OpenAI is projected to reach $34.7 billion by the end of December 2025.

The Vision Fund unit recorded an investment gain of 3.5 trillion yen this quarter, primarily from the OpenAI stake, contributing to the company’s best quarterly result since July-September 2022, compared with 1.18 trillion yen in the same period last year.

Despite the gains, investors are cautious about the sustainability of such returns. Sources told Reuters in October that OpenAI’s losses are mounting, even as its valuation has climbed steadily throughout the year.

“There are various opinions, but SoftBank’s position is that the risk of not investing is far greater than the risk of investing,” Goto said.

To fund its AI ambitions, SoftBank has employed a range of fundraising measures. These include the Nvidia sale, a $9.17 billion partial stake sale in T-Mobile, bond issuances totaling over $4 billion, and bridging loans of $8.5 billion for OpenAI and $6.5 billion for the pending acquisition of semiconductor design firm Ampere.

Masayoshi Son, SoftBank’s founder and CEO, is known for making leveraged bets on transformative technologies. His track record includes both high-profile wins, such as an early investment in Alibaba, and notable missteps, including WeWork. With AI now at the center of his strategy, the global investment community is closely watching whether SoftBank can continue its winning streak.