Shares of SoftBank Group surged 11.8% to ¥5,590 after the company locked in pricing on the largest retail bond ever sold by a Japanese corporation — a ¥1 trillion ($6.3 billion) seven-year note carrying a 4.75% coupon. With subscriptions opening today, the market is treating the deal as proof that Masayoshi Son can still fund his enormous AI ambitions. But the financing raises as many questions as it answers.

  • The Coupon Is Generous — Because It Has to Be. The 4.75% rate is the highest on SoftBank's straight bonds in 17 years.

The average coupon on yen-denominated retail corporate bonds issued in Japan this year was just 2.3% , meaning SoftBank is paying more than double the market average to attract buyers. Analysts say banks were reluctant to take the risk, leaving the deal dependent on retail investors — ordinary Japanese households effectively becoming lenders of last resort for Son's AI wager.

  • Even ¥1 Trillion Doesn't Close the Funding Gap. This is SoftBank's third retail bond offering this year, having raised ¥418 billion in April and ¥260 billion in June, while the company has committed to investing a total of $64.6 billion in OpenAI alone.

Even ¥1 trillion doesn't close the gap — Bloomberg Intelligence's Sharon Chen says a shortfall above $20 billion remains, making offshore issuance likely in the near term. Investors cheering today's rally should expect more dilutive debt ahead.

  • The Balance Sheet Has Buffers — For Now. SoftBank reported ¥40.1 trillion in net asset value, a 17% loan-to-value ratio, and ¥3.5 trillion in cash at March 31, 2026.

The 13% LTV (a measure of how much debt a company carries relative to the value of what it owns) remains well below its 25% self-imposed ceiling. But the company faces ¥497.9 billion of bonds maturing in September and a $40 billion OpenAI-linked bridge loan due in March 2027 , which could compress those buffers fast.

  • The AI Bet Is Getting Bigger, Not Smaller. SoftBank posted its best result ever — annual net profit of around ¥5 trillion ($32 billion) for the year to end-March 2026 — driven primarily by the rising valuation of OpenAI. That profit is largely paper gains, not cash. Meanwhile, SoftBank has pledged a 75-billion-euro ($87 billion) program to build AI data centers in France alone , on top of the U.S. Stargate project. The stock's rally reflects confidence that Son's vision is working, but the financing treadmill is accelerating alongside it.