Everyone has a guardian angel...except Soobin. No he has a guardian demon and it deals with things in a much more violent fashion, but also much more effective. But nonetheless, he was an angel living his best life with Soobin. An unexpected terror strikes both their worlds, with billions of lives are at stake. Yeonjun, Soobin and their friends are some of their counterparts are the only ones who can find the key to their victory. But as they say, nothing goes their way, deaths, betrayal, and yet love blossoms in their new lives. Will they ultimately succeed...or will it be the end of the world?