To LOVE-Ru (2008)

They're Not Illegal Aliens...But They Are From Outer Space And Of Rather Questionable Moral Character

The story is about Rito Yuuki , a high-school boy 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.