From Sapphire Sky:
Nishina Yukito, who is the only boy in a family of girls, moved out of his house in hopes of a peaceful life. One day, he sees something strange on the roof of the school. It's a spaceship and a mysterious girl with a crown emerges. She introduces herself as the imperial Princess Lacey of Planet Kura-ura, who claims that she is searching for the White Rabbit, who is supposed to help her fulfill the wishes of ten humans... and Yukito is the rabbit?!