This dissertation is a synthesis of social, political, and international histories of decolonization in Korea and Japan. My study demonstrates how the liberation of Korea became a foundational historical event not only for the colonized but also for metropolitan society. Despite the recent emphasis on the need to treat the metropole and colony as one analytical field, scholars have yet to approach decolonization as a mutually constitutive process that restructures both the metropole and the colony. The fields of Area Studies and International History often divide their focus on the regional aftermath of the Japanese empire into separate national units of analysis, resulting in histories split between the U.S. and Soviet occupations of Korea (19451948) and the U.S. (Allied) occupation of Japan (1945-1952). In a radical departure from the more nation-centered scholarship, my work treats post-empire Japan and Korea, U.S. occupation policy in Japan and Korea, and Japanese and South Korean anti-Communist regimes as one analytical field. In order to maintain a focused line of inquiry through the complexity of the decolonizing world, I position the Korean postcolonial population in Japan, or the so-called "Korean minority question," as a primary methodological site in my work. With such an analytical focus, I pose a key set of different questions that turn our attention to the transnational processes of dismantling the Japanese empire. First, how did the problem of repatriating both Korean colonial conscripted workers from Japan and Japanese colonial settlers from Korea molded popular nationalistic sentiments and mutual antagonisms in post-empire Japanese-Korean relations? Second, how did post-1945 everyday encounters between the Japanese and Koreans, the defeated and the liberated, frame the Japanese "embracing" of defeat and colonial independence along with U.S. occupation? And third, how did the politics of Korean diasporic nationalism emerge in Japan from the struggle over self-determination and autonomy from Japanese power and how did it develop into the critical locus of U.S.-Japan-South Korea cold war containment policy? By exploring these issues previously overlooked in the existing historiography, my work offers a new framework that overcomes a dichotomy and separation between histories of post-1945 Japan and Korea.