Is there such thing as a race concept in Japan?
Race is looked at as an outdated concept by most of the Japanese citizens. History shows that it did not use to be the case; I have heard that ethnic korean immigrants used to be victimised during natural disasters, in the early days.
Japanese citizens are not exactly mono-ethnic; there are those descend from Ainu (mixed with immigrants from the West through Russia) in the north, and those mixed with Koreans and Mongolians in the South. Then there is Okinawa, that used to be a different kingdom. While some Ainu activists want them to be considered a different race, I have never met a Japanese person who thinks they are a different group. The term "Japanese" is based more on culture than race, I feel. I have met some old people who know about their descent, but they think they are the same race as the rest of Japanese because everyone came from somewhere in the early days.