The anthology Japan's household registration system and citizenship: Koseki, identification and documentation, David Chapman and Karl Jakob Krogness, eds. (Routledge 2014) provides a first, extensive, and critical overview of Japan's koseki system. Situated from the seventh century Taika Reforms until today at the center of Japanese governance and society, the koseki opens up for comprehensive and deep exploration the Japanese state, family, and individual, as well as questions relating to citizenship, nationality, and identity. The scope of potential koseki-related research is extensive and is relevant for many disciplines including history, sociology, law, ethnography, anthropology, cultural studies, literature and media studies, gender and queer studies. Given the koseki's origins in the household registration regimes of China and its subsequent influence on the household registration systems of Korea and Taiwan during the colonial period, the koseki also opens the way for comparative studies within and beyond East Asia.