So I lived there for 5+ years, and my wife is Korea who lived in Japan.
There is a very large and real anti-korean sentiment/prejudice in Japan.
I mean a few years ago now, but there was a bunch of anti-korean protests in shin okubo. https://japantoday.com/category/features/kuchikomi/nasty-nat...
And there's the whole 'Zainichi' thing, who are still systematically oppressed.