Sumire is a shy blonde girl who meets Azusa, Ui and Jun after Yui and the others graduate. She is a freshman, two years below the other light music club members. She is currently working in the Kotobuki household as a maid and originally came to the light music room to try to retrieve Tsumugi's teaset that was left behind after she graduated. After being scared off a few times by Sawako, she eventually agrees to join the light music club and eventually becomes its drummer. Similar to Tsumugi, she is quite talented at preparing tea, but feels inclined to keep her role as a maid a secret from the others due to the fear of being punished by Tsumugi.