The story revolves around Rito Yuki, a high-school student who cannot confess to the girl of his dreams, Haruna Sairenji. One day when coming home and sulking in the bathtub, a mysterious, nude girl appears out of nowhere. Her name is Lala and she comes from the planet Deviluke, where she is the heir to the throne. Her father wants her to return to her home planet so she can marry one of the husband candidates. But she decides that she wants to marry Rito in order to stay on Earth. Commander Zastin has been ordered to bring Lala back and has already battled Rito. He reports to the emperor that Rito would be suited to marry Lala, after hearing Rito, who was actually defending himself instead of Lala, say that marriage is impossible unless it is with the person you love. Lala truly falls in love with Rito and decides that she wants to marry Rito after hearing what he said. Her father decides that, if Rito is able to protect Lala from her fiancés, then he can marry her. However, if Rito ...