This chapter examines the fluctuating characteristics of Japan as a regional power in Asia since the end of World War II, arguing that Japan’s regional influence cannot be understood through a static definition. Rather, it requires recognition of the nuanced development of its role and capabilities from the postwar period onward. In this respect, Japan does not purely align with the category of regional and global powers defined in this book as “exerting influence principally within their home regions” and “consequential states in the international system.” While it has often exerted, and continues to exert, influence in shaping regional and global rules and norms within an evolving strategic environment, Japan’s strategic scope remains more confined to Asia, particularly East Asia, amid shifts in both its material and ideational capabilities.