When I was stationed in Japan in the mid 60's. I took karate at a dojo in downtown Kokura. One of my fellow servicemen was a Korean-American, when he tried to join the class, the head honcho wouldn't accept him.
It was strange to me at the time. You'd ocassionally meet Japanese who still held grudges against the Americans for WW2, but the bad blood between the Japanese and Koreans was much more easy to see.