The Fatal Encounter

Won Ryu Hwan (Kim Soo Hyun) is a highly skilled North Korean special forces agent who is sent down to South Korea to aid in a mission to reunify the two Koreas. Going deep undercover, Ryu Hwan becomes Dong Gu, the neighborhood idiot in Seoul.

He spends three years in solitude, perfecting every trip and stumble. Suddenly he's joined by two other agents: his rival Lee Hae Rang (Park Ki Woong) disguised as an aspiring K-pop star, and Lee Hae Jin (Lee Hyun Woo), disguised as a high school student.

When the North decides that all the undercover agents must be eliminated right away for the sake of peace, it becomes a fight for survival as the three agents are unwilling to lose the happy ordinary life that they managed to have for a short time.