I don't know too much, but I know that they have laws that state that anyone who's a citizen is treated equally regardless of ethnicity. yet there are some xenophobic groups that actively hate on S/N Koreans who migrated there, along with some Chinese.
They kind of treat their immigrants like trash. But we're talking about a group of people. Not everyone in Japan holds these views. I had japanese friends when I lived in japan and we couldn't speak a word to eachother. Then you'd have some adults that would scream and shout at you.
one time my dad's car broke down in the rain. A Japanese guy in a expensive car in a business suit got out to come help him. Once he saw he was not Japanese, he immediately turned around and got back in and drove off. He got out in the RAIN to help, and changed his mind once he saw my dad's ethnicity.