Tens of thousands of impoverished Korean tenant farmers moved to Japan to find work . There , they faced difficult working conditions , discrimination , government surveillance , and vigilante violence . The Japanese government was anxious about the potentially destabilizing effect of Korean laborers in Japan ; yet , because Koreans were legally Japanese nationals , it could not explicitly restrict immigration from Korea . Instead , during economic downturns in Japan , colonial police in Pusan were instructed to restrict Korean emigration on an informal basis by limiting access to travel documents ( 旅行証明書 ) . In Japan , Koreans came under the jurisdiction of the Japanese government proper , rather than the Government General of Korea . This meant that they were governed by Japanese law and had greater civil and political rights — notably the right to hold meetings and vote in national elections — than Koreans in Korea . Political rights were especially important to the community of Korean students in Japan . See Koreans in Japan . After the 1923 Great Kantō earthquake , the Japanese government pursued a more active policy of assimilation towards Koreans in Japan . Primary school attendance was made compulsory in 1930 , as was membership in the . This organization , tightly controlled by the Naimusho and the Government General of Korea , issued identity cards to its members , controlled the travel of Koreans between Korea and Japan , and organized labor mobilization , as well as sponsoring the cultural , social and ideological activities typical of other " voluntary " associations
1923 Great Kantō earthquake
1923 Great Kantō earthquake
History of Japanese nationality