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https://en.m.wikipedia.org/wiki/Ethnic_issues_in_Japan
The Japanese Constitution states that "there shall be no discrimination in political, economic or social relations because of race." At least one native people-group (the Ainu) was formally recognized by the Japanese government for the first time in 1997. However, non-citizens who were born in Japan or elsewhere can be legally restricted from certain services and activities.[1][not in citation given] According to census statistics, 98.5% of the population of Japan are Japanese, with the remainder being foreign nationals residing in Japan.[2] However, these statistics measure citizenship, not ethnicity, with all domestic minorities such as the Ainu, Ryukyuans, Burakumin, Hafu, and naturalized immigrants being counted as simply "Japanese."[3] The Japanese government refuses to collect data on the ethnic identities of its citizens, claiming that there are no issues of race relations among Japanese citizens as they are all of the same race.[4]
In 2010, according to the UN Committee on the Elimination of Racial Discrimination, Japan's record on racism has improved, but there is still room for progress.[86] The committee was critical of the lack of anti-hate speech legislation in the country and the treatment of Japanese minorities and its large Korean and Chinese communities
Only Wikipedia, I'll concede. You might want to ask why Japan is populated by people of Japanese ethnicity to the turn of 99%. As I understand it, the country has no immigration program at all. This is despite one of the, if not the, oldest population in the world. The country's population is reducing and this will speed up. Immigration would help revitalise the country, but they won't do it. Why? Severe xenophobia is my belief, but I welcome contradiction.
Off topic I know, but you asked.