From the publisher: As the second largest contributor to the UN budget, Japan is expected to play a role in implementing the Responsibility to Protect (R2P). Why has Japan been unenthusiastic about actively engaging in the R2P discourse? What is the impact, both domestic and international, of incorporating R2P in its diplomatic agenda? In examining these questions, we first identify different perceptions about R2P among policy-makers and civil society in Japan. We then analyze the post-Cold War politics of diplomatic initiatives concerning Japan’s human security doctrine. Third, we assess opportunities (and limitations) of synchronizing R2P with Japanese diplomatic agendas. Throughout the article, we argue that rather than distancing itself from R2P, as typically seen in official statements, actively embracing R2P may provide greater benefits for Japan both in terms of enhancing its diplomatic influence and mobilizing domestic political support.