Sumire is a shy blonde girl who meets Azusa, Ui and Jun after Yui and the others graduate. She is a freshmen, 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. As her family, who came from Austria were taken in by the Kotobuki household before she was born, Sumire grew up as Tsumugi's playmate, often regarding her as her older sister and inadvertently sparking Tsumugi's interest in yuri by introducing her to manga of that genre. As she grew up and learned the truth about the relation between the two families, Sumire felt she needed to regard Tsumugi with more respect while in public. Sawako reveals that Tsumugi asked that the tea sets be left in the club room. However, before the beginning of the new term Tsumugi had asked Sumire to remove the tea sets thereby ensuring that Sumire would encounter the other members of the light music club and would be invited to join. Sumire's situation is revealed to the surprise of the other members of the club by Sawako.