North Korea's South-bound Special Operations Unit 5446 is a gathering of elites, with a selection rate of 20,000:1. They include the most outstanding elite member Yuan Liuhuan, the son of the top cadre of the Republic, Li Hailang, and the youngest South-bound spy in the history of the Republic, Li Haizhen. The three are known as the legends of the 5446 Unit. The three came to South Korea with the great mission of reunification of the motherland. One disguised himself as a fool in the slums, one transformed into a young man who aspired to be a singer, and one became a high school student. In the time when there was no mission assigned, they personally experienced the miserable life of the lowest class and felt a lot. However, what fate will they usher in?