The trend of global energy shortage has accelerated nuclear installation construction in many countries. However, once a nuclear accident occurs, it may cause serious risks and long-term environmental damage. The occurrence of the Fukushima nuclear disaster raises important questions about what Ulrich Beck termed the “risk society.” Particularly, Japan's subsequent nuclear wastewater discharge plan links the nuclear risk of the installation country with the marine environmental risk of neighboring countries and, ultimately, all mankind, raising not only many potential marine environmental conflicts but also justice questions about which communities should bear the risks and liabilities. However, the existing international legal system addressing liability and compensation issues in nuclear accidents is mainly the product of the post-Chernobyl era. Confronted with the potential marine pollution caused by Japan's radioactive wastewater discharge, the deficiencies embedded in the existing international legal system limit not only the adequate relief of transboundary victims but also the ability of humankind to effectively manage the risk of marine nuclear pollution. From a legal perspective, this article provides transboundary relief as a lens through which to examine whether the existing institutional framework has achieved the objective of effectively managing risks and explores possible ways to address Japan's nuclear wastewater discharge and similar group risks that might arise in the future.