Isana descended to the human world to obtain his angel wings and needs the help of a young boy named Aiba Subaru. As his partner, Subaru's heart will determine if Isana becomes an angel or a devil. Since Subaru is such an honest and kind boy, the task seems easy at first. However, Subaru is kind to a fault, often harming himself for the sake of others. Although these traits will gain his wings faster, Isana is bothered by Subaru's extreme selfless behavior and can't help but interfere in spite of his own personal interests.