Secretly, Greatly

Three North Korean spies who infiltrate South Korea as a village idiot, a rock musician, and a high school student, respectively. They assimilate to small town life while awaiting their orders, until one day, due to a sudden power shift in the North, their mission turns out to be an order to commit suicide.The film is based on the 2010 spy webtoon series Covertness by Hun, which has received over 40 million page hits (wikipedia)