This review paper provides preliminary analysis and answers to three key questions that were identified by synthesizing qualitative evidence from climate security research in Japan. The questions identified are: (1) Has Japan participated in the global climate security debate at all? (2) Why did climate security struggle to become a major political theme in Japan until 2020? (3) Why did Japan explicitly start dealing with climate security as a policy issue in 2020? We identify and discuss four key reasons relative to the second question. The review provides key details (and general parameters) of these questions that have been overlooked by not only Japanese researchers but also climate security research conducted between 2017 and 2022 in Europe and the United States. Climate security suddenly became a trending topic among Japanese researchers and political elites in 2020; we find evidence that future studies could provide important and more robust insight if an analysis of the above questions is supported by interview data obtained from Japanese government officials. In doing so, researchers will be able to provide valuable insight into the possibility (and extent) that inter-ministerial rivalry between key ministries has impeded domestic progress on climate security action. Furthermore, three separate projects on climate security have been commissioned and recently implemented in Japan. These form the basis for this first systematic literature review of 34 papers and the related research reports resulting from these projects. These papers and reports were retrieved from the electronic databases of Google Scholar, ProQuest, and the National Institute for Environmental Studies in April 2022. While the main limitation of this review paper is that readers are expected to connect these questions to their own experiences at the global level, we reduce the possibility of presenting biased information by identifying and verifying missing details. For example, we had difficulty identifying the method used in one of the co-authored papers and contacted the corresponding author. In summary, sustained discussion in academia and high-politics settings should eventually lead to a greater awareness about climate security.