SoftBank's market capitalization surpasses 43 trillion yen, with the OpenAI IPO expected to boost stock prices by 40% in one week

SoftBank's stock price today (26th) rose 7.55% in a single day on the Tokyo market, with a market value surpassing 43 trillion yen, a cumulative increase of over 40% in a week; the driving forces come from rumors of OpenAI IPO heating up, and its subsidiary SB Energy, focused on power infrastructure, announcing plans to secretly apply for an IPO in the U.S.
(Background: The largest single-round funding in history: OpenAI completed a $122 billion fundraising, with a valuation soaring past $852 billion)
(Additional context: SoftBank pledged OpenAI shares for a $10 billion loan, with Masayoshi Son betting on AI with leverage)

Known for "betting on the future of technology," SoftBank's stock surged 7.55% today (26th) in Tokyo, breaking through 43 trillion yen in market value, and even more astonishingly, a total increase of over 40% within a week.

The imagination space of 40 trillion yen

The core driver behind this rally is that OpenAI is preparing to submit an IPO application soon. Bloomberg pointed out that the news of OpenAI's IPO has caused the market to boil, because once OpenAI goes public, the long-standing issue of opaque valuation in AI investment circles—those relying on "latest funding round valuations"—will face the first market-based pricing test.

Takashi Nakagawa, senior analyst at Tokai Tokyo Research Institute, told Bloomberg that the market has been eagerly awaiting OpenAI's IPO, which might soon become a reality, "extremely exciting," but he also added, "Currently, the stock price is purely driven by expectations. I still want to see how OpenAI's market value ultimately stabilizes."

Meanwhile, SB Energy, a subsidiary of SoftBank focused on power generation and grid management, also announced plans to secretly apply for an IPO in the U.S.

Over the past year, SB Energy has raised more than $1.8 billion from SoftBank, OpenAI, and asset management firm Ares Management, making it a core piece in Masayoshi Son's deployment of data centers in the U.S. Both companies signaling IPO plans at the same time effectively bring SoftBank's "hidden assets" to the surface.

Leverage bet of $65 billion

SoftBank is one of OpenAI's largest shareholders, with a committed total investment approaching $65 billion, and is expected to acquire about 13% of ChatGPT's developer this October.

Last year, SoftBank participated in OpenAI's largest single-round funding of $122 billion, with a valuation reaching $850 billion at that time. Now, if OpenAI goes public, this paper investment will be priced by the market, rather than relying solely on private valuations.

Bloomberg also pointed out that one of the past market concerns about OpenAI was the continuous rise of competitors like Anthropic, Google's Gemini, Elon Musk's xAI, which diluted OpenAI's moat narrative. This rally shows that the IPO news has reassured some investors about OpenAI's market position, and this confidence is directly reflected in SoftBank's stock price.

But Takashi Nakagawa's words are worth reserving: "It's purely expectations at this point." OpenAI has not yet formally filed for an IPO, and SB Energy's application is also a "secret submission," meaning all key figures—revenue, losses, pathways—are still in a black box.

The reason IPO excites the market is precisely because it means this black box is about to open. But what we see after it opens will be the real test.