Tamaki Otoya is the last in a line of ancient summoners tasked to battle evil forces that threaten mankind. Burdened by his duty as a summoner, Tamaki has always found strength from his childhood friend, Asahi, with whom he has a deep, emotional bond. So when Asahi's friend is found out to be possessed by a demon, he awakens--as the one destined to exorcise demons out of tortured human souls.