Rito Yuuki is a bumbling boy who wants nothing more than to confess his love to the lovely Haruna, but a variety of obstacles always seems to stand in his way. One day, while relaxing in his bathtub Rito found his hands full - literally - with the breasts of a strange alien girl named Lala who suddenly appeared in his lap! She is the princess of Planet Deviluke, and she has run away from home to escape the prospect of an arranged marriage; and unfortunately for Rito, his accidental groping is the traditional engagement ritual of his otherworldly guest! Deviluke's emperor will destroy Earth if Rito backs down from his "proposal," but all he really wants to do is be with Saruyama! Naked antics, magical powers, misunderstandings, Lala's marriage-happy family and Rito's own shyness are many of the barriers he must face in his attempt to win the real love of his life – that is, if Lala doesn't win him over first!