Rito Yüki is a fifteen-year-old boy who has tried to confess to the girl whom he loves, Haruna Sairenji, numerous times but has been unable to do so through the strangest of circumstances. Meanwhile, a mysterious extraterrestrial girl named Lala Satalin Deviluke runs away to Earth in order to avoid daily arranged marriage candidate interviews set up by her father, the king of her home planet, Deviluke, as well as Emperor of the Milky Way Galaxy and Ruler of the known universe. Using one of her own inventions, she teleports naked into Rito's bathtub, where he accidentally gropes her breasts...