An up and coming idol whose CD "reached the top of the charts in just one week." She is a childhood friend of Yuu. She calls Yuu "Niko-kun" and he refers to her as "Tama-chan."
Fuuka is a big fan of her music, to the extent that listening to one of her songs makes her emotional enough to cry. One of Koyuki's songs was used as the theme for a popular movie ("Half & Half," a clever reference to another manga by the same mangaka.)
Though his sisters tease him that she would never respond to him if he contacted her now that she is famous, in reality she sent Yuu a message on Twitter.