South Korea in the 1960s is remembered as an era marked by the rapid development of science and technology, as well as the growth of the domestic economy. Histori-ans of science have described the meaningful advancement of science during this period as a result of the establishment of a Korean science and technology system that overturned Japanese colonial precedents and sought support from U.S. science policy. In this study, however, I seek to understand the scientific achievement of South Korea in the 1960s by circumventing the binary scheme advocating either the continuity of, or departure from, colonial precedents. To that end, I shall explore Korean geneticist Kang Yung Sun’s academic career, and his ongoing connections with the Japanese scientific community, from 1941 to 1968. I argue that Kang’s sci-entific achievement in human genetics can be understood as an outcome of his efforts to develop new postcolonial relationships among U.S., Japanese, and Korean geneti-cists, by way of his colonial connections to a network of Japanese geneticists. Throughout the paper, I demonstrate that focusing on connections and exchanges among scientists beyond national borders can afford historians of science an oppor-tunity to investigate scientific activities and trends in the 1960s, without sustaining the binary scheme of continuation or rupture.