This research project explored the legal and political dimensions of energy transition conflicts, focusing on how states and societies respond to contestation around nuclear and renewable energy development. By adopting a comparative lens centered on Japan, France, and Germany, the project examined how legal mobilization, litigation strategies, and multi-level governance mechanisms shape energy policymaking in contested contexts. Particular attention was given to the role of strategic litigation in driving institutional change, reframing public debates, and challenging dominant policy narratives in Japan. The study revealed how litigation can function not only as a reactive legal tool but also as a proactive mode of engagement that pressures political institutions and regulatory frameworks. In Japan, the legacy of the Fukushima disaster and the recent acceleration of nuclear restarts—justified through climate, sovereignty, and cost-efficiency arguments—highlighted the evolving legal and political stakes of energy governance. The project also engaged with theoretical debates on legalism by revisiting Japanese socio-legal literature on gendai-gata soshō (Tanaka 1996) and seido kaikaku soshō (Awaji 2012), using these frameworks to analyze recent energy-related cases as part of broader institutional reform dynamics. Empirical case studies were supported by fieldwork and interviews in Tōhoku, as well as document analysis of litigation and regulatory procedures. As part of the project’s dissemination strategy, a major international symposium was organized in November 2024 at Waseda University, titled Energy Transitions Litigation in France, Japan, and Germany in collaboration with CNRS, Waseda University, FernUniversität in Hagen, Utokyo, Kyoto University. The event brought together scholars, practitioners, and activists from all three countries to discuss litigation as a mode of democratic accountability and policy influence. Research outcomes were also presented at multiple international workshops and conferences, helping to position the project within broader interdisciplinary debates on energy justice, climate governance, and strategic litigation. A peer-reviewed journal article and a book chapter are currently under review, and further publications are planned to consolidate the project’s findings and contribute to academic and policy debates on energy transition governance.