To Love Ru(2008)

Rito Yuuki is unlucky when it comes to love — no matter how hard he tries to confess to his crush, his efforts end in failure. After another day’s confession goes down the drain, Rito spends his night sulking in his bathtub. But when a naked girl with a pointed tail teleports into the tub with him, it seems like Rito’s luck is finally looking up! His fortune doesn’t last long when he finds himself accidentally engaged to the buxom beauty who is none other than the princess of the planet Deviluke!