Invasion by demons in the human world began to increase rapidly. The attacks appears to be a sign that the sealed away Demon King, Shout, will soon be revived. Standing up against the demon army that suddenly invaded the peaceful human world, Holy Knight Luvilias confronts Shout’s son and the new Demon King, Vois. Vois becomes obsessed with Luvilia and makes it his new goal to turn her into his slave. With the help of Tia the evil goddess, Iris the succubus and Vois’s younger sister, and Lifulia the witch, Vois plans on forcing Luvilias, the empire’s strongest knight, to submit to his will and to use her power to keep his father sealed so that he may continue his rule as the Demon King.