Heaven has obliged its youthful angels to dwell and study among mankind for ages in order to become full-fledged angels. This is also true for top-of-the-class Gabriel White Tenma, who feels it is her destiny to be a magnificent angel who brings happiness to mankind. On Earth, however, Gabriel becomes hooked to video games and finally becomes a hikikomori. She declares herself a "Fallen Angel," and is uninterested in anything else, much to the chagrin of Vignette April Tsukinose, a demon whom Gabriel met during her heavenly early days on Earth. Vignette's attempts to restore Gabriel to her former self are futile, as Gabriel rejects any attempt to disrupt her beloved lifestyle. They encounter two eccentrics during their tenure on Earth.