In this opening chapter, the author discusses the nature of states and nationality, and whether, in an age of globalization and cyberspace, it is even meaningful any longer to talk about national borders. It is noted that the movement of people is a phenomenon as old as human history itself, and that in comparison, the system of sovereign states that mutually recognize each other’s defined territorial sovereignty has a much shorter history. The author provides an overview of migration flows, whilst enumerating the various reasons people have for migrating from one region to another, and the historical tragedies and triumphs often involved. He notes that immigration, though high on the political agenda in Western societies, is not a central political issue in Japan at the moment, but challenges the view that Japan is an unusually xenophobic country or, conversely, that it has remarkably maintained its cultural homogeneity. This chapter also lays out the structure of the whole volume.