Based on the erotic doujin game by Daijobi Kenkyuujo (ダイジョビ研究所).

Standing up against the demon army that suddenly invaded the peaceful human world, Knight Luvilia confronts the Demon King, Vois. With the Demon God, Tia, Vois defeats Luvilia and makes her into his property. Luvilia shouts and cries telling him to stop but can’t stop moaning from the intense stimulation. Vois enjoys his victory by indulging in the finest of women. When he’s done though, she teleports away. In preparation for their next battle, Vois adds his little succubus who is also his younger sister, Ilis, and big-breast loli witch, Lufilia to his team.