Rito Yuuki, a shy 16-year-old, has yet to declare his love for Haruna Sairenji, a classmate and the object of his adoration since junior high. Unfortunately, his predicament becomes much more difficult when a mysterious, nude female crashes into a swimming Rito one night. Rito is further perplexed when he learns that the girl, Lala Satalin Deviluke, is the crown princess of an extraterrestrial nation who has fled her country. Despite her status as the heiress of the galaxy's most powerful empire, Lala is more than eager to marry the seemingly ordinary Rito in order to escape an unpleasant political marriage.