Shares of SoftBank Group Corp., led by legendary investor Masayoshi Son, soared more than 11% after its telecommunications subsidiary raised its full-year profit forecast, with the market capitalization hovering near $173 billion. The stock closed up 10.68% in Tuesday's trading session. Growing optimism around Arm Holdings, the chip design leader acquired by SoftBank, has further fueled investor confidence in SoftBank's potential to occupy a central position in the artificial intelligence sector through strategic holdings. Combined with expectations that Japan's ruling government, led by Sanae Takaichi, will implement larger-scale economic stimulus measures, these factors drove a sharp rally in SoftBank's share price.

The latest surge in SoftBank's stock price, along with the resulting expansion in market value, significantly advances Masayoshi Son's AI vision toward reality. This momentum is not accidental but is built on years of strategic investment in AI computing infrastructure and core computational capabilities closely tied to data center CPUs. In particular, SoftBank's portfolio investments in Arm Holdings, Graphcore, Ampere Computing, and a recent major stake in OpenAI reflect a full-stack strategy spanning from underlying AI hardware architecture to computing infrastructure clusters and AI application layers.

The single-day stock surge of over 10% underscores increasing market recognition of Son's AI ambitions. According to the latest earnings report, SoftBank's telecom subsidiary, SoftBank Corp., reported a better-than-expected 8% year-over-year increase in revenue for the first nine months of fiscal 2025, reaching a record ¥5.2 trillion. Operating profit also rose 8% to ¥884 billion. Bolstered by this strong performance, the telecom unit raised its full-year revenue outlook from ¥6.7 trillion to ¥6.95 trillion and lifted its operating profit target to ¥1.02 trillion.

Despite minor adjustments in consumer-focused operations to prioritize long-term profitability over subscriber growth, SoftBank Corp. stated that its fiscal 2025 targets are being exceeded. Consumer-related revenue grew 3%, while operating profit in that segment increased 6%, even as smartphone subscriptions fell by approximately 100,000 in the third quarter due to tightened customer acquisition policies.

Andrew Jackson, a senior Japanese equity strategist at Ortus Advisors, noted that the strong rebound in Arm Holdings' share price has also provided a bullish tailwind for SoftBank, given the latter's substantial stake in the UK-based chip design giant. SoftBank holds nearly 90% of Arm, whose architecture is widely used across consumer electronics and increasingly serves as the foundation for server CPUs.

Masayoshi Son has stated that through SoftBank's majority stake in Arm, full ownership of UK AI chip designer Graphcore Ltd., and the recent acquisition of Ampere, SoftBank will hold key technologies within the global AI computing infrastructure ecosystem.

Arm CEO Rene Haas remarked in a recent earnings call, “Our data center-related royalty revenue more than doubled year-over-year. We expect data center operations to become our largest business in the coming years, marking a major milestone as it surpasses mobile chip revenue.” The company also plans to supply CPU architecture for over half of the data center server clusters used by major cloud providers like Google, Microsoft, and Amazon by year-end.

Although Arm fell short of overly optimistic analyst expectations for licensing revenue, it still posted record quarterly revenue of $1.242 billion in the final quarter of fiscal 2025, beating consensus estimates compiled by LSEG, driven by strong AI computing demand.

Ampere, recently acquired by SoftBank, designs high-performance, low-power server CPUs based on Arm architecture specifically for cloud and data center use. With Ampere and Arm under its umbrella, SoftBank is positioned to build one of the world's most influential server CPU ecosystems, accelerating Son's AI vision.

Ampere focuses on “Cloud Native Processors” and “Sustainable AI Compute” for cloud-native and large-scale AI data centers, emphasizing higher rack density and lower power consumption for equivalent computing performance. Its product lineup includes Ampere Altra, an 80-core server CPU; Ampere Altra Max, a 128-core version for hyperscale data centers; and AmpereOne, a 5nm processor with future roadmaps supporting up to 256 cores.

Arm has emerged as one of the biggest beneficiaries of the AI boom. Nvidia's Grace CPU, Amazon's Graviton server processor, Google's Axion Processors, and Microsoft's Azure Cobalt 100 all utilize Arm architecture, signaling its evolution from a mobile-focused technology to a foundational element of AI cloud infrastructure.

The reduced instruction set computing (RISC) architecture used by Arm offers significant energy efficiency advantages over Intel's x86 architecture, particularly for AI inference and training tasks in data centers. In the era of generative AI and AI agents, Arm's Neoverse architecture can deliver up to 3.5 times more performance per watt than traditional x86 processors in cloud and data center workloads. As cloud giants like Amazon, Google, and Microsoft continue heavy investment in AI data centers, a portion of that spending is expected to flow toward Arm-based server CPUs.

For SoftBank, rising share prices, strong profits from its telecom unit, and the addition of Ampere reinforce growth expectations for Masayoshi Son's long-term AI infrastructure and ecosystem strategy. The 69-year-old founder envisions SoftBank playing a role in the global AI landscape comparable to Nvidia, leveraging early successes such as the Alibaba investment to capture returns from the AI boom.

Key elements of this strategy include Arm, in which SoftBank holds a 90% stake; recently acquired Ampere; UK AI chip firm Graphcore; participation in the $500 billion “Stargate” data center project in partnership with OpenAI, Oracle, and Abu Dhabi’s MGX; and major long-term investments in AI leaders like OpenAI and TSMC.

The recent upward trajectory in SoftBank's stock price reflects strong market confidence in the company's positioning within foundational AI infrastructure and core technology—a vision aligned with Son's AI blueprint to build a global ecosystem encompassing chip IP, CPU architecture, AI computing platforms, data center infrastructure, and leading AI applications.

SoftBank's investments in Arm, OpenAI, and Ampere illustrate a comprehensive approach spanning underlying AI technology, computing infrastructure, and application layers. Arm serves as a core architecture provider for mobile devices and an expanding number of data center server CPUs, while Ampere strengthens SoftBank's control over the AI computing chain from IP to implementation.

SoftBank's official AI strategy emphasizes that these investments form part of a multi-layered approach—including Arm, Stargate, Ampere, and OpenAI—designed to create synergies and foster growth within a vast “SoftBank AI ecosystem,” ranging from chip architecture and design to AI platforms and models.