The Kingdom of Sound exists in a dimension where fairies thrive, depending on music from the human world to power their magical energy. Regrettably, an increasing number of human songs are created without pure intentions, leading the fairies to suffer from a shortage of pure magical energy. Worried about her kingdom, the queen instructs her daughter to travel to the human world and find individuals with vocal potential who can share their voices and restore balance to the dimension. The queen's daughter, Princess Alto, succeeds in locating three young schoolgirls attending Hinoura Elementary School who might be able to assist her. These girls are Kanon Kohinata, a cheerful girl who loves singing and possesses an exceptionally healing voice; Marika Amano, a prideful girl whose voice is so skilled that it rivals Kanon's; and Kodama Yagi, a careful girl with a soft voice that harmonizes well with her friends. Upon meeting, the girls and the fairy princess form a friendship and set a goal to become an idol group. But will these girls manage to achieve fame and save the Kingdom of Sound?