In a world where demons rise from hell to ravage the human realm, humanity’s only hope are the Holy Knights, warriors who wield holy blades. However, the Holy Knight’s leadership is corrupt and has is disliked by most of the Holy Knight’s ranks. Adio, a prodigious Holy Knight, voices his discontent, only to be cast aside. This leads Adio to take up arms against his former organization, with the help of a fallen angel.