Earth Tremors(1980)

Ju Yeong-nbok volunteers to work for the North Korean army as a Russian translator. As the political climate in the North deteriorates, his sister flees south. Yeong-bok is worried that her defection will prevent his being promoted in the ranks of the communist party. He breaks up with his girlfriend because she is catholic in order to prove his party loyalty, but Yeong-bok still finds himself blacklisted.