The angel Karasu comes to Earth on a mission to convince a demon, Shirasagi, to return to Hell. But Shirasagi is nothing like his wicked peers. He lives in an abandoned bar and is a practicing priest so that he can realize his one wish: to seek redemption from God and turn into a human.

Karasu lets Shirasagi off the hook, as he is no ordinary angel either. Although he is one of the Powers—warrior angels tasked with maintaining the natural order—he consistently doubts the existence of God and his own purpose in life. As two misfits, these supernatural beings grow close and strike up an unlikely relationship. To escape their binding chains, Karasu and Shirasagi are prepared to do whatever it takes to protect the other; however, that same love may just become their doom.