Trailer for Secretly Greatly.
Won Ryu-Hwan (Kim Soo-Hyun) trained in the North Korean Special Forces. He can speak five languages and is also a lethal killing machine. Two years ago, he received orders to deploy to South Korea as a spy. While wondering in a poor neighborhood in Seoul, Won Ryu-Hwan passed out and was awakened by a worried old mother. The woman then allowed him to live in a small apartment above her modest convenient store and let him work in her store. His identity in South Korea is now Bang Dong-Gu and he has taken up the persona of a goofy, mentally challenged young man. Since that time, Bang Dong-Gu has gotten to know everybody in the neighborhood and has become attached to the woman who treats him like her second son.
One evening, Bang Dong-Gu receives a visitor in his small apartment. His visitor is Lee Hae-Rang (Park Ki-Woong), who trained in the same North Korean Special Forces Unit. Lee Hae-Rang has also received orders from North Korea to work covertly as a spy in South Korea. His persona is that of a young wannabe rock star. Lee Hae-Rang finds it difficult, because he never played the guitar before. Shortly later, Ri Hae-Jin (Lee Hyun-Woo), also a member of their special forces team in North Korea, arrives in the same neighborhood. While the three young men live unnoticed among their neighbors, they await orders from North Korea. Their order finally arrives.