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SoftBank Group’s shares fell 6.9% in Tokyo on Thursday, October 22, and closed at ¥4,305. That is half their record close of ¥8,632 on June 2. Masayoshi Son’s company is now worth about ¥24.7 trillion ($157 billion), Bloomberg reported, which puts it behind Hitachi and Recruit Holdings in Japan.
In June, SoftBank had just passed Toyota as Japan’s most valuable company. The reversal matters beyond Tokyo because SoftBank is OpenAI’s biggest outside backer. Much of that bet runs on borrowed money, and the borrowing is getting more expensive.
What the slide has cost, in yen and dollars
The “halved” headline holds up on closing prices. From the intraday high of ¥9,074 on June 2, the fall is closer to 53%. The table uses daily closes and Bloomberg’s current valuation. The peak value is our own estimate from the share price.
| June 2 peak | October 22 close | Change | |
|---|---|---|---|
| Share price | ¥8,632 | ¥4,305 | −50.1% |
| Market value (yen) | about ¥49.3 trillion | ¥24.7 trillion | about −¥24.6 trillion |
| Market value (dollars) | about $309 billion | about $157 billion | about −$152 billion |
On June 1, the day SoftBank overtook Toyota, Jiji Press put its value at ¥48.78 trillion. The stock rose again the next day.
October has done much of the damage. Shares closed September at ¥6,430, so they are down 33% this month, the worst showing in the Nikkei 225. The stock now trades below its split-adjusted close at the end of 2025 (¥4,400). The whole 2026 rally is gone.
Credit markets moved first
Bond investors got nervous well before shareholders did. On Tuesday, October 20, five-year credit-default swaps on SoftBank debt hit 432 basis points, according to Bloomberg data. That is the highest since early November 2022.
These contracts insure bondholders against a default. In June they cost about 280 basis points.
For a while, the two markets told different stories. In early October Bloomberg reported that stock investors were looking past the credit risk to the upside in AI. This month they stopped.
The trigger was a wider scare about AI debt. Bonds of US data-center operator CoreWeave fell to distressed levels last week. The selling then spread to other companies that fund AI spending with debt.
“SoftBank’s vulnerability stands out as investors increasingly scrutinize the financial health of AI-related companies,” Kazuyuki Muramatsu, head of investment management at Nagomi Capital, told Bloomberg.
The borrowing behind the OpenAI bet
SoftBank has committed $64.6 billion to OpenAI, which will give it roughly 13% of the ChatGPT maker. That commitment alone equals about 41% of SoftBank’s market value today. Much of the cash came from new debt.
- Junk bonds: In September SoftBank sold $11.1 billion of bonds rated below investment grade. It was the largest high-yield corporate bond sale on record, Reuters and Bloomberg reported. The dollar notes pay 8.625% to 9.75%, against 2.125% to 5.25% on a 2021 sale.
- Margin loans: In September SoftBank raised its loan against Arm Holdings shares to $25 billion, Bloomberg reported. In August it signed a $10 billion loan against its OpenAI stake.
- Bridge financing: It took a $40 billion bridge loan in March for the OpenAI stake, which it plans to repay, according to Bloomberg.
Margin loans are the part to watch. Shares secure them, so a sharp fall in Arm or a lower OpenAI valuation can force a borrower to post more collateral. The same tool sits behind other AI fortunes, as BreezyScroll found when Larry Ellison pledged $9.2 billion in Oracle shares. It works well while prices rise.
A delayed OpenAI IPO leaves no quick payoff
Investors had hoped public listings would hand SoftBank cash and a market price for its biggest bets. Those listings have slipped. Delays to the OpenAI and SB Energy IPOs dented those hopes, Reuters reported in September. OpenAI is now raising money privately, and Anthropic looks set to list first.
Bloomberg also pointed to cheaper Chinese AI models as a threat to OpenAI’s pricing power.
None of this means SoftBank is near default. It owns far more than its OpenAI stake, chiefly control of Arm, and it booked a record ¥5 trillion net profit for the year to March. But the market now prices SoftBank as a debt-funded bet on one private company. That is the kind of AI correction Fitch warned about in September.
The next hard numbers arrive on November 10, when SoftBank reports results for the six months to September. They will show what the OpenAI stake is worth on its books and how much debt the September deals added.