A young girl named Nowa dies from a prolonged illness at the age of ten, never having had the chance to experience a normal school life. Upon her death, she is invited not to the afterlife she expected, but to a school in heaven called Angel Academy. In this celestial institution, young souls train to become full-fledged angels, working in pairs to graduate. Nowa is initially overjoyed at the prospect of finally going to school. However, her excitement turns to confusion when she discovers she has been partnered with the one remaining unpaired student, a boy who is feared by the others and referred to as a demon due to his selfish and unruly behavior. His name is Nto. The story follows this unlikely pair as they navigate classes, try to work together despite their opposite natures, and learn what it truly means to become guardian angels. The setting is a whimsical rendition of heaven, complete with a formal academy where angels-in-training live and study. The ongoing narrative arc focuses on the development of the main duo as they face challenges that test their patience and force them to confront their own shortcomings, moving from discord to a tentative partnership.