Professor Ito Abito who is an anthropologist at University of Tokyo, wrote the following.

When the Yamato Court ( 4th AD-6th AD ) came to prevail throughout the archipelago, a sense of indigenous identity, gradually manifested itself in the islands’ inhabitants. At the same time, however, the inhabitants of the farther fringes of the archipelago during the early period of the Yamato state appear in records under independent names, as ethnic minorities. On the other hand, one could also say that by incorporating local ethnic minorities on the northern and southern peripheries under their rule, they have, in effect voluntarily relinquished their racial homogeneity. One could also say that in the effort to further unity by making the ethnic minorities thus incorporated under their rule into subjects under an emperor system, the illusion of a uniform, homogeneous single race was elevated into a kind of national ideal. In Japan following the Meiji Restoration, which sought to create a modern state and society stressing the correspondence between the concept of race and awareness of the land and the nation, the ethnic identity of the Ainu and the Ryûkyûans has in a sense been denied.

From this point of view, Japanese people tend to play down all the difference that characterised Japanese society to emphasise an homogenisation that is unreal and imaginary. Now, it is not difficult to understand how the Ainu were considered ‘Japanese’, although less civilised, but still part of Japanese ethnicity. However, these are not the only factors that have helped Japan to develop this peculiar attitude towards border and national identity.