This dude Yoshiyuki loves to work out. He also loves sex, cause he's not dead. Now that he's a teacher at an all-girls school, he gets to combine his two favorite things. He decides to give his struggling students some private tuition, AKA, his dick - cause that certainly won't be hard to grasp.
Karen and Mizuki are magical Utea girls who protect the world from evil aliens. How do they go about doing that? By letting the beasts fuck their brains out of course!