For centuries, Heaven has required its young angels to live and study among humans in order to become full-fledged angels. This is no different for top-of-her-class Gabriel White Tenma, who believes it is her mission to be a great angel who will bring happiness to mankind. However, Gabriel grows addicted to video games on Earth and eventually becomes a hikikomori. Proclaiming herself a "Faillen Angel," she is apathetic to everything else—much to the annoyance of Vignette April Tsukinose, a demon whom Gabriel befriended in her angelic early days on Earth.