Rito keeps trying to confess to the girl he actually likes, but he's engaged to an alien princess, and the show finds comedy in that specific misery every single episode. The fanservice isn't window dressing, it's the actual plot engine, the thing that keeps throwing obstacles between him and what he wants. Nothing here pretends to be deep, which is why it works: you watch a guy get increasingly tangled in romantic chaos and laugh at how thoroughly the universe is conspiring against him.

Rito Yuuki has never caught a break with romance. He is too timid to confess to his classmate Haruna Sairenji, and after another failed attempt he sulks in the bathtub at night. That changes when a naked girl with a pointed tail suddenly appears in the tub with him. She is Lala, heir to the throne of the planet Deviluke, and she has run away to escape an unwanted political marriage. Through a misunderstanding, Rito ends up engaged to her. Now he must protect Lala from her other suitors, while a growing crowd of adoring girls keeps wrecking his chances with Haruna. Expect a sci-fi romantic comedy full of slapstick and lewd ecchi gags.