Mitsui & Co., Ltd. ("Mitsui", Head Office: Tokyo, President and CEO: Kenichi Hori,) has subscribed to a third-party allotment of new shares by Commonwealth Fusion Systems LLC ("CFS"), a U.S.-based fusion energy company, through a consortium of 12 Japanese companies (the "Japanese Consortium"^*1). This marks Mitsui's second investment in the fusion energy field, following its investment in Kyoto Fusioneering Ltd. announced on May 17, 2023.

Fusion is a process in which two light atomic nuclei combine to generate enormous amounts of energy—based on the same principle that powers the sun—which can be harnessed for electricity generation. It is expected to become a sustainable energy source that does not emit CO₂. The hydrogen isotopes used as fuel can be derived from seawater and other sources, eliminating concerns about resource depletion or geographical concentration. Unlike nuclear power generation through fission, fusion does not involve chain reactions and does not produce high-level radioactive waste. Japan's Fusion Energy Innovation Strategy, revised in June 2025, emphasizes the importance of public–private collaboration and targets the demonstration of power generation by the 2030s. With the rapid increase in electricity demand driven by breakthroughs in AI and other advanced technologies, expectations for fusion energy as a promising option to ensure stable future power supply are rising worldwide.

CFS, a spin-off company of MIT (Massachusetts Institute of Technology), is the world's leading and largest private fusion company, utilizing the magnetic confinement system (tokamak type)^*2. The company plans to build the world's first commercial fusion power plant "ARC" in Virginia in the United States, with the intent of generating electricity in the early 2030s. In June of this year, CFS announced that it signed a power purchase agreement with Google for 200 megawatts of electricity from its first ARC power plant.

The Japanese Consortium will acquire technical and commercial expertise in policy, regulatory, and the development, construction, operation, and maintenance of ARC from CFS's commercialization projects in the United States. In addition, each consortium will bring together its know-how and expertise and aspire to expedite the commercialization and industrialization of fusion energy power generation in Japan.
The collaboration between the Japanese Consortium and CFS is complementary to the Japan – U.S. joint partnership to accelerate the development and commercialization of fusion energy power generation in Japan and the United States and represents a strong commitment and growing momentum toward the early realization of commercialization in both countries.

Mitsui is committed to building a society in harmony with the environment, by providing a wide range of low-carbon solutions through collaboration with partners, cross-industry alliances, and engagement with innovative technologies. In the field of fusion energy. Mitsui will continue to accumulate cutting-edge knowledge and expertise through collaboration with stakeholders, including those in industries related to CFS, and contribute to the practical application and industrialization of fusion technologies.

*1 Mitsui & Co., Ltd.; Mitsubishi Corporation; The Kansai Electric Power Co., Inc.; JERA Co., Inc.; Mitsui O.S.K. Lines Ltd.; JGC Japan Corporation; Development Bank of Japan Inc.; NTT, Inc.; Fujikura Ltd.; Sumitomo Mitsui Banking Corporation; Sumitomo Mitsui Trust Bank Ltd.; and Mitsui Fudosan Co., Ltd.
*2 A torus-shaped fusion energy device that uses a strong magnetic field to confine ultra-high temperature plasma.

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