This paper outlines the historical background to Korean migration and Japanese colonialism in order to understand the birth and formation of the Korean population in Japan (Zainichi Koreans). Through this exploration, this paper shows how Japan attempted to assimilate the Koreans into the bottom of Japanese society and to destroy their ethnic identity as Koreans. It also examines how the racial discourse of the Japanese ‘superior race’ had been developed and played an integral part in justifying its socio-economic and subjugation of East Asian people including Koreans during the colonial period.