Japan's Household Registration System (koseki seido) is an extremely powerful state instrument, and is socially entrenched with a long history of population governance, social control and the maintenance of social order. By looking through the lens of the koseki system, the book takes both an historical as well as a contemporary approach to understanding Japanese society. In doing so, it develops our understanding of contemporary Japan within the historical context of population management and social control; reveals the social effects and influence of the koseki system throughout its history; and presents new insights into citizenship, nationality and identity.