Singing and dreaming together, a talented singer-songwriter and a same-aged keyboardist add harmony and love to each other's lives.

Dong-hyun is a high school student. One day, he falls from the rooftop and bumps into Pan-soo who is a passerby. Pan-soo is a member of a criminal organization. When the two men wake up in the hospital, they discover that they have switched bodies.

Peaceful unification between North and South Korea is about to take place. Therefore, the DMZ area near Panmunjom (JSA) will be designated as a Special Peaceful Zone (a.k.a SPZ) for unification of the Korean Commonwealth. So, Panmunjom has entered a overall development phase. However, murder takes place in the DMZ. The suspect is a deserter who is only known as code-name Firefox, the special agent of North Korea.