SoftBank's Record Short Book Meets Its Heaviest Borrowing Calendar

Short interest in SoftBank climbed to 2.27% of free float, the highest since July 2025, as the group weighs a $10-20 billion junk bond sale.

SoftBank Group has spent September doing two things at once: retiring old debt and lining up new debt. The scale of both has caught the attention of traders, who have built the largest bearish wager against the Japanese conglomerate in more than a decade — just as it prepares to ask credit markets for billions more.

Short interest as a share of free float climbed to 2.27% by Wednesday, the highest reading since July 2025, according to Bloomberg. In notional terms that works out to $3.9 billion, a level not seen since at least early 2015. For a company that has lately made headlines mostly for acquisitions and multi-billion-dollar loans, the positioning is a striking counterpoint.

A rally that invites contrarians

The stock has been on a tear. Over seven days it has gained 21%, and across 30 days it is up 19%. At €36.71 on Friday, the shares were essentially flat against Thursday's close of €36.70, a move of 0.04%. That advance explains part of the appeal for short sellers: after a run of that size, betting on a pullback becomes tempting.

It also explains the risk they are carrying. Should the shares keep climbing, bearish traders will be forced to buy back stock to close their positions — and that buying pressure can accelerate the very rally they are betting against. This is the classic short-squeeze mechanism, and it accounts for part of the recent price action without any single fundamental catalyst behind it. SoftBank's market capitalization stands at roughly €209.09 billion.

Momentum gauges flash caution. The relative strength index sits at 69.7, a reading that points to overbought conditions, while annualized 30-day volatility of 61% underscores how jittery trading has become.

The repayment that started the week

On Monday, September 15, SoftBank retired the full outstanding balance of $25.9 billion from a loan originally taken out to fund its OpenAI commitment. A complete repayment of that size would normally read as a show of balance-sheet strength.

It lands in the middle of a broader financing push. On September 4, the group placed a retail bond worth ¥1 trillion, or about $6.3 billion. The seven-year notes carried a 4.75% coupon — the top end of an initially targeted range of 4.3% to 4.9%. That outcome suggests investors demanded a meaningful risk premium for their exposure.

New York roadshow, junk-bond ambitions

A far larger capital-markets operation is now in preparation. From September 14 to 17, SoftBank is gauging investor appetite in New York for a possible dollar-denominated junk bond, with CFO Yoshimitsu Goto and other executives attending meetings at Citigroup's offices. A volume of $10 billion to $20 billion is under discussion, and a euro tranche is also conceivable.

The funding need traces back to a $40 billion bridge facility already secured to backstop investments in OpenAI. If upcoming stakes are indeed financed with borrowed money, SoftBank's gross debt could rise from around $80 billion in March 2025 to more than $130 billion.

What the shorts are weighing

The combination of swelling short positions and ongoing debt raising raises the question of how durable investor confidence really is.

As of June 23, SoftBank put its net asset value at ¥74 trillion, equivalent to ¥13,000 per share — a figure the stock's supporters routinely cite as evidence of undervaluation. The group remains in expansion mode on the deal front as well, including the roughly $4 billion acquisition of DigitalBridge agreed in December.

Market skepticism has shown up in the price too. On Thursday the stock closed at €36.61, down 2.6% from the previous day. Even so, the seven- and 30-day gains of roughly 20% and 19% respectively mean the shares had enjoyed a powerful run before that recent softness set in. The RSI of 68.6 points to buying momentum that is already well advanced, while annualized 30-day volatility of 64% captures the nervousness surrounding the name.

The trillion-yen endgame

Strategically, SoftBank sketched out its target picture back in June. It aims for a net asset value of ¥1 quadrillion by 2042, starting from ¥74 trillion as of June 23 — a planned tenfold increase over 16 years, built on four pillars: AI models through the OpenAI partnership, semiconductors via Arm, AI infrastructure in the form of data centers in the United States, France and Japan, and robotics.

The next quarterly results are scheduled for November 5. Until then, the question of whether short sellers are forced to unwind further is likely to keep shaping the share price — and the answer will arrive in the same stretch that SoftBank closes one financing chapter and opens another.