Four Angels (Semi Cho Ryu, Aiden, Nerissa and Leah) and four Demons/Demons (Steven, Danien, Lake and Robin) are sent to Earth in an unused area of Golden College, where they learn everything they need to become Guardian Angels and Guardian Demons. The Angels and Demons are required to form pairs as part of their education, each of whom will have to deal with a human being, known as Earthlings, and help them choose between the right and wrong path in life without being discovered. Angels and Demons cannot operate simultaneously, so they decide, in a confrontation in the Challenge Room, who will work first. Additionally, they are subject to V.E.T.O.
