The four fairies, Kururu, Chiriri, Sarara, and Hororo, live inside small bottles and go to the human world. Why are they in bottles? Because in the human world, wishes are written on paper and sent floating in bottles. So the fairies thought that, instead of letters, they would put themselves in bottles and have their wishes granted. So what is their wish? It is to become human. There are many things the four do not know of the human world though. They are taught various things by Sensei-san and grow little by little. As their big discoveries and small mistakes are watched over every day... Source: AnimeNfo