Due to his father's new job, Yahiro-kun was forced to move with his sister IO-Chan to a new apartment. They quickly adapted to the new home and began to get used to independent life. However, shortly after enrolling in the Academy of Ahira noticed a strange large truck outside his home. Things IO-Chan have long arrived and he began to wonder what was going on. Having risen to the top on ladder and in fear, that in unlocked room can be the robber, Yahiro became on the sly open the door. There he met a half-naked girl dressed only in underwear, zealously pushing a heavy piano. Seeing our hero, the girl screamed and forced him to leave. A little later she dressed in a beautiful dress and came out to say Hello. Her name was Ruria Fondina and she was a Princess of one of the island States. The girl came to live with our hero. Soon other "princesses"began to appear at Yahiro's door.