it's extremely weird. I lived in Japan for a very long time and it's completely normal to them to prefer to live among other Japanese people.
"OF COURSE you're uncomfortable around lots of people who are not similar to yourself"
as long as you're melanistic that's considered cultural pride. it's only if you're white that it's racist.
but white nationalism usually implies that you want to forcibly expel/do violence to people who aren't white. I don't support violence except in extreme cases.