Commitment (2013) on Netflix

Plot summary

Myung-hoon, nineteen, grew up in privilege in North Korea and dreamed of becoming a pianist. When his father, a spy, dies disgraced, he and his younger sister Hye-in are sent to a forced labor camp. Colonel Moon, his father's superior, offers a way out: go South as an assassin and finish what his father failed to do, and his sister will be released. Myung-hoon agrees and undergoes two years of training. He reaches South Korea posing as a defector, is taken in by a couple who are North Korean spies, and enrolls at a high school. There he befriends Hye-in, a bullied classmate who shares his sister's name and wants to dance professionally. His orders are to find and eliminate Big Dipper, an agent working for a rival faction.