Commonwealth Fusion Systems, the Massachusetts-based nuclear-fusion start-up, has secured new capital from a consortium of 12 Japanese companies led by trading houses Mitsui & Co. and Mitsubishi Corp., according to reports from Nikkei and other outlets on 28 August. The stake is part of CFS’s $863 million Series B2 round, which the company says will speed development of its fusion technology and advance plans for a commercial reactor later this decade. While individual allocations were not disclosed, Nikkei said the Japanese group will provide “several tens of billions of yen,” marking the first time Japanese corporates have taken equity in CFS. The partners aim to collaborate on component procurement and share know-how across their respective supply chains. The deal deepens U.S.–Japan cooperation on next-generation clean energy and underscores mounting private-sector interest in fusion, a field that promises carbon-free baseload power but still faces formidable engineering and regulatory hurdles before large-scale deployment.