In an increasingly globalized world, international migration has to be seen as a complement to other flows and exchanges taking place between countries. During the last two decades or so, the issue of migration has emerged as one of the most serious crises in industrialized nations. The main reason for this is that, in an era of growing economic globalization, when each state is moving towards border-free economic spaces in the world order, the flow of migrants is largely determined by a global labour market, being more or less impervious to governmental policies. It is ultimately impossible to intensify border controls to keep migrants out, so any attempts by government to restrict the entry of migrants result in the growth of an illegal foreign migrant population. The existence of illegal migrants itself demonstrates an erosion of the state's sovereignty.
One significant phenomenon in relation to foreign migrants, both legal and illegal, is that they often continue to stay, regardless of the workforce needs, and make a measurable demographic difference to the population of the host country. This is illustrated by the emergence of various problems in relation to their needs for housing, employment and welfare. As a result, a variety of the country's existing infrastructural systems are affected and are forcibly changed into those that are capable of accepting those foreign migrant workers into society as ordinary 'residents'. This situation further creates conflict within a country between its exclusive authority to control the entry of non-nationals and its obligation to protect 'residents' within its territory.
Japan is traditionally considered to be one of those countries which does not facilitate citizenship acquisition and, therefore, does not encourage immigration. Japanese citizenship relies on jus sanguinis principles, which confer citizenship on the basis of descent regardless of the place of birth. Lineage is regarded as the primary determinant of 'Japaneseness' and is viewed as the major element to form the collective identity of the Japanese people. Indeed, the country is generally recognized for its high homogeneity in ethnicity, language, religion, class and culture. This high homogeneity together with the Japanese collective identity, which puts a relatively strong emphasis on the maintenance of cultural uniformity, the importance of the group, and an ethic of harmony, is often seen as a