This chapter examines the transnational activism born out of Japan’s domestic experience with industrial pollution as a possible new frontier in the study of Japan. The chapter suggests that a transnational-environmental perspective can help us know the country in novel ways. For instance, Japan’s recent environmental history reveals fascinating processes of ‘grassroots regionalisation’ and ‘grassroots globalisation’ operating as formative elements in postwar civic movements and civil society. It also reveals Japanese activists as influential actors in regional and global environmental initiatives. Moreover knowledge of Japan’s experience with industrial pollution and other environmental challenges can potentially enrich our understanding of these issues within our own backyards and globally. The chapter argues that one departure point for producing new knowledge on Japan may lie in a conceptual liquification of the rigid borders of the country and an embrace of regional and global perspectives.