South Korean government did not support Koreans living in Japan Whereas North Korean government even though isolated state were poor They were  years ahead of South Korean government regarding to helping Koreans living in Japan This is basic reason why majority of Koreans living in Japan went to North Korean government run schools More then  percent Koreans living in Japan were born in island province of  Chejudo But more then half of them affiliate themselves with North Korean schools Main reason is North Korean government helped Koreans in Japan in very very tough time wherease South Korean government did nothing Koreans living in Japan dont really like to divide themselves into North or South Korean political alliance Majority of them consider themselves as Korean from Southern Korea but they had no choice to preserve Korean cultural identity majority of them went to North Korean government run schools  If you combine Sakalin Island Korean population Korean population in Japan probably would be about  million  Korean mixed KoreanJapanese mixed KoreanRussian populations