Since the dawn of Earth’s existence, angels from the planet Eden have observed humanity—whom they call “Earthians”—to evaluate their virtues and flaws. Chihaya and Kagetsuya are two such agents assigned to carry out this mission. However, despite his orders, Chihaya often becomes personally involved in the lives of humans, much to Kagetsuya’s frustration.
As Chihaya continues his work, he also begins to question the origin of his mysterious black wings, leading him deeper into a series of unfolding secrets.