To Love Ru (Volumes 1-2)

Yuuki Rito is your average high school student--awkward, shy, and hopeless when it comes to confessing his feelings to the girl of his dreams. But one day, a beautiful woman suddenly materializes in his bathtub! Her name is Lala Deviluke, an alien princess on the run from an intergalactic empire. After Rito gets unwittingly engaged to Lala, he soon finds himself sucked into a battle for Lala's affections, as alien suitors from across the galaxy vie for her hand in marriage. Rito's troubles have only just begun!