Development of Japan’s First*1 Underground Data Center Utilizing an Existing Tunnel
—Next-Generation Infrastructure Site to Be Established in Kobe City,
Hyogo Prefecture, with Operations Scheduled to Begin at the End of 2027—

October 6, 2026
Mitsui Fudosan Co., Ltd.
Kumagai Gumi Co., Ltd.
Getworks Co., Ltd.

Key Points of this Press Release

• Promoting Japan’s first*1 underground data center project utilizing an existing tunnel in Kobe City, Hyogo Prefecture
• Establishing a data center that achieves both energy efficiency and high physical security by leveraging the characteristics of underground space, thereby meeting growing demand in the generative AI era and the increasing need for infrastructure to securely store and manage critical data
• Aiming to develop underground data centers at multiple locations nationwide by using underutilized assets such as tunnels and former mine sites, beginning with the Kobe project, and pave the way for creating new value for local communities

Tokyo, Japan, October 6, 2026 - Mitsui Fudosan Co., Ltd., a leading global real estate company headquartered in Tokyo (hereafter, “Mitsui Fudosan”), Kumagai Gumi Co., Ltd. (hereafter, “Kumagai Gumi”), and Getworks Co., Ltd. (hereafter, “Getworks”) (collectively, “the Project Partners”) announced today that they will begin developing Japan’s first*1 underground data center (hereafter, “the Project”) by utilizing a tunnel*2 that Kobe City used until September 2005 to transport soil for land development (hereafter, “the Existing Tunnel”).

In the Project, an underutilized asset will be transformed into new digital infrastructure in the form of a data center by bringing together the Project Partners’ expertise and technologies while leveraging the characteristics of the Existing Tunnel, including its naturally cool temperatures*3, high seismic resistance, and excellent physical security due to its limited external access. The creation of this digital infrastructure will address rapidly growing demand for graphics processing unit (GPU) servers and the rising need for infrastructure to securely store and manage critical data.

Rendering of Japan’s first*1 underground data center utilizing an existing tunnel

• 1 Japan’s first commercial data center project to be developed by utilizing existing tunnel space to provide services to external customers (as of September 2026, based on research by Mitsui Fudosan).
• 2 The tunnel is a former belt conveyor tunnel of world-class scale, stretching approximately 9 miles (14.5 km) between Kobe’s mountains and sea. Since it began operating, the tunnel has played a key role in Kobe’s development—famously described as “the mountains going to the sea”—including the development of residential and industrial parks and land reclamation for Kobe Airport. On September 4, 2026, Mitsui Fudosan and Kumagai Gumi were named the successful bidders in a conditional tender for the lease of the tunnel. The section of the tunnel covered by the tender is approximately 1.9 miles (3 km) long, with an area of approximately 182,986 ft² (17,000 m²).
• 3 The temperature inside the tunnel has been confirmed to remain between 59°F and 68°F (15°C–20°C) throughout the year.

■ Changes in the Environment Surrounding Data Centers and Providing a New Data Center Option

Demand for GPU servers with high computing power has been growing worldwide alongside the rapid adoption of generative AI technology. Meanwhile, Japan faces infrastructure development challenges due to factors such as the need to secure land and electricity for data centers, soaring construction costs, and a shortage of facilities capable of accommodating high-heat-generating GPU servers. In addition, given the need to protect critical data and strengthen their ability to respond to natural disasters, companies and local governments have a growing need for data centers with high physical security and resilience.

Against this backdrop, Mitsui Fudosan focused on underground space that has not been fully utilized to date. It arrived at the idea for the Project based on the belief that the characteristics of underground space, such as its naturally cool temperatures, seismic resistance, and physical security, are well suited to the requirements of data centers in the AI era. In addition, Mitsui Fudosan believes that using existing underground space can reduce the environmental impact of construction and shorten the time required for commercialization. Leveraging these characteristics, Mitsui Fudosan will propose a new option for data centers to society.

Overseas, data centers are being developed using underground facilities, former mine sites, former military facilities, and other sites. A wide range of businesses are increasingly using these data centers, whose strengths lie in their high physical security and resilience to disasters. Through this project, Mitsui Fudosan will promote the use of underground space as a new option for data centers in Japan, while helping to establish sustainable and resilient digital infrastructure.

■Eyeing Data Center Development at Multiple Locations Using Underutilized Underground Space Nationwide

Throughout Japan, there are underground spaces that are not fully utilized, such as tunnels and former mine sites that have served their purpose. Mitsui Fudosan believes that a key priority is to find new uses for such underutilized assets and use them to create new value for local communities.

Mitsui Fudosan sees this project as the first step toward a new model for using underutilized underground spaces that exist across Japan. Leveraging the development, operational, and technical expertise to be gained through the Project, Mitsui Fudosan aims to develop underground data centers at multiple locations nationwide, using underutilized underground space such as tunnels and former mine sites.

By transforming local community assets that have not been fully utilized into new social infrastructure for the AI era, Mitsui Fudosan will address the social issue of how to make effective use of underutilized assets while also developing sustainable digital infrastructure. In doing so, Mitsui Fudosan aims to help solve local community issues and create new industrial value.

Project concept image

■ Project Development Overview—Operations Scheduled to Begin at the End of 2027

In the Project, Mitsui Fudosan, working together with Kumagai Gumi and Getworks, will install container data center facilities in the Existing Tunnel, which is located deep underground*1. In the future, the Project aims to operate the facility as a data center with a maximum power receiving capacity of approximately 20 megawatts.

In the initial development phase, services are scheduled to begin at the end of 2027. The facility will support the latest GPU servers that are required in the generative AI era and make maximum use of existing resources, including through the introduction of a water-cooling system that recirculates groundwater, thereby reducing environmental impact and achieving highly efficient operations.

Furthermore, the Project will utilize the shelter-type container data center*2 technology deployed by Getworks, in addition to the high seismic resistance and excellent physical security offered by underground space, to enhance its ability to respond to natural disasters and external risks. The Project aims to establish highly resilient digital infrastructure that can also accommodate the storage of critical data held by companies, local governments, and other entities.

Rendering of a shelter-type container data center*2 specialized for large-scale disaster and emergency preparedness

Container data center installed by Getworks in Yuzawa Town, Niigata Prefecture

• 1 Most of the Existing Tunnel is located at a depth of approximately 131 ft (approx. 40 m) or more below ground.
• 2 Getworks has completed the development of a shelter-type container data center designed for large-scale disasters and other emergencies. Manufactured entirely in Japan, the product incorporates earthquake-resistant and impact-resistant features, as well as measures against electromagnetic pulses (EMP). https://prtimes.jp/main/html/rd/p/000000027.000141706.html (in Japanese)

■Comments from the Project Partners

■About the Mitsui Fudosan Group’s MAG!C Business Proposal Program

The MAG!C business proposal program was established in fiscal 2018. The program is designed to take the individual visions of Mitsui Fudosan Group employees and, by engaging the company at large, elevate them through the stages of conceptualization and realization. Through this innovation, the program aims to position Mitsui Fudosan as an industry developer platform that goes beyond the boundaries of a real estate developer. Within this framework, in principle, the original proposer takes the role of business lead and personally drives the proposed initiative.

The Project originated from the desire to create new value through the use of underground space, an underutilized asset, and contribute to the sustainable development of local communities. The Project was developed by the original proposer through the MAG!C program.

■Introduction of the Project Partners and Cooperating Company

Since its founding, Kumagai Gumi has been involved in the development of numerous social infrastructure projects, including tunnels, dams, railways, and roads, and has an extensive track record and advanced technical capabilities in the fields of civil engineering and building construction. In recent years, in addition to the infrastructure field, the company has also been engaged in renewable energy and other businesses aimed at solving emerging social issues.

Kumagai Gumi Co., Ltd.
Headquarters: Shinjuku-ku, Tokyo; President and Representative Director: Shin Ueda
https://www.kumagaigumi.co.jp/en/

Getworks has been engaged in the planning, design, construction, and operation of container data centers since 2013. With a cumulative track record of 380 units built as of September 2026, the company is working to develop next-generation digital infrastructure in fields including AI and high-performance computing (HPC) through container data centers that enable rapid construction and flexible expansion in line with customer needs.

Getworks Co., Ltd.
Headquarters: Chiyoda-ku, Tokyo; Representative Director: Hidenori Nakazawa
https://www.getworks.co.jp/(in Japanese)

Pacific Consultants is a social infrastructure services company. As a leading construction consulting firm for more than 70 years since its founding, it has been deeply involved in social infrastructure development and urban development in Japan and overseas—including cities, buildings, railways, roads, airports, ports, rivers, and water and sewerage systems—covering everything from project conception and surveys to planning, design, construction supervision, and maintenance. Under its vision of “Producing the Future,” the company provides new value to society with the aim of realizing a sustainable society in which everyone can live with peace of mind.

Pacific Consultants Co., Ltd.
Headquarters: Chiyoda-ku, Tokyo; Representative Director, President Executive Officer: Satoko Okano
https://en.pacific.co.jp/

■ Sustainability in the Mitsui Fudosan Group

Based on the meaning of its “& mark,” “to generate new value with society through cooperation, coexistence and co-creation, we forge ahead, innovating,” the Mitsui Fudosan Group views the “creation of social value” and the “creation of economic value” as two wheels of a cart. Accordingly, we believe that the creation of social value leads to the creation of economic value, and that this economic value then creates even greater social value.

Moreover, we identified six Group Materiality priority issues when formulating our new management philosophy in April 2024. These Group Materiality priority issues are (1) Contribute to industrial competitiveness, (2) Coexist with the environment, (3) Health and Vitality, (4) Safety and security, (5) Diversity and inclusion, and (6) Compliance and governance. The Mitsui Fudosan Group will work to address each of the materialities through its core business activities and contribute to the promotion of sustainability.

(References)
・ Group Management Philosophy and Long-Term Vision
https://www.mitsuifudosan.co.jp/english/corporate/innovation2030/
・ Group Materiality
https://www.mitsuifudosan.co.jp/english/esg_csr/approach/materiality/