Kyō Mekui is a high school student who tends to skip school due to a trauma in his past. Kyō secretly creates songs using vocal song synthesis software as his hobby. Three girls who just entered fifth grade — the crybaby Jun "Jun-tan" Gotō, the strong-willed Nozomi "Zomi" Momijidani, and the somewhat sleepy Sora "Kū" Kaneshiro who takes life at her own pace — email Kyō. These three girls, who were raised together like sisters since childhood, want Kyō to help them break into music.