SoftBank’s Arm Stake Now Exceeds Net Debt as OpenAI Frenzy Drives Stock to Multi-Year Highs

SoftBank's $165B Arm stake towers over $122.9B net debt; record $31.4B profit and $25B OpenAI gain drive stock surge of 56%.

SoftBank Group Corp. has crossed a pivotal financial threshold that fundamentally alters how the market views its risk profile: the value of its controlling stake in chip designer Arm Holdings now surpasses the conglomerate’s entire net debt. Arm’s roughly 90% holding is worth approximately $165 billion, towering over net debt of $122.9 billion. Analysts see this as a powerful buffer that gives founder Masayoshi Son greater latitude to pursue his aggressive, AI-centric investment strategy even in turbulent markets.

The milestone emerged from SoftBank’s fiscal 2025 results, which showed a record net profit of $31.4 billion — the highest ever reported by a Japanese company. While the fourth quarter produced an operating loss of $2.88 billion, mark-to-market gains on the Arm stake and stabilizing valuations within the Vision Fund have reshaped the group’s liquidity profile. The changing math helps explain why investors sent SoftBank shares soaring 11.89% on Friday to close at ¥6,757 on the Tokyo Stock Exchange, bringing the five-day gain to roughly 25%.

The rally has been supercharged by SoftBank’s expanding bet on OpenAI. Over the past fiscal year, the group poured $32.4 billion into the artificial intelligence developer, with an additional $30 billion commitment — $10 billion of which was delivered in April. By October 2026, total exposure will reach $64.6 billion, securing SoftBank a roughly 13% stake. The value of that position has ballooned: OpenAI’s valuation jumped from $150 billion at the end of 2024 to $730 billion in February 2026, and talk of a $1 trillion IPO valuation is growing louder. Market chatter suggests OpenAI could file its SEC paperwork as early as May, with a listing slated for September 2026. SoftBank alone booked a $25 billion paper gain on the stake in the quarter ended March 2026.

Arm itself added fuel to the fire, with its shares climbing 16% on Friday after Nvidia’s strong earnings and the unveiling of a new “Arm AGI CPU” architecture. On the operational side, SoftBank’s telecommunications unit struck a healthcare alliance with Sumitomo Mitsui Financial Group and Fujitsu to build a sovereign cloud-based platform powered by proprietary language models. The initiative targets 60 million users and 4,000 medical facilities, leveraging existing PayPay and LINE ecosystems.

Meanwhile, SoftBank is pressing ahead with portfolio monetisation. It has confidentially filed a prospectus for the US initial public offering of its renewable energy subsidiary SB Energy. The timing is favourable given the record profit and the bullish sentiment around AI-related assets. The company also continues to execute a $6.5 billion share buyback programme, of which about $4 billion had been used in fiscal 2025. Management has signalled it will keep repurchasing shares as long as the stock trades at a discount to the group’s estimated net asset value of roughly $300 billion.

Despite the stock’s 56% surge over the past 90 days, the trailing price-to-earnings ratio sits at just 7.7 — well below the sector average of 17.2. Some models peg the fair value at ¥4,498.7, far below Friday’s close, but the market is clearly pricing in a hefty AI premium. Another measure using a different earnings base puts the P/E at 10.8x, above the five-year average of 6.8x, confirming that the premium is substantial.

The stock is now testing its 52-week high of ¥6,924, just shy of its all-time peak of ¥6,923.8. The relative strength index for Arm shares is flirting with overbought territory, which could inject more volatility into SoftBank’s near-term trajectory. Analyst ratings remain predominantly bullish: eight “Strong Buy”, three “Hold”, and one “Strong Sell”. Yet the ultimate catalysts — Arm’s continued market performance and the timing of the OpenAI IPO — lie outside SoftBank’s direct control. With the race for AI supremacy between OpenAI and Anthropic far from decided, the stakes for Masayoshi Son’s conglomerate have never been higher.