Sawako Yamanaka (山(やま)中(なか) さわ子(こ) Yamanaka Sawako) is a teacher at Sakura High. She was originally the adviser of the wind instrument club but then she was forced to become the adviser of the light music club by Yui, Mio, Ritsu and Mugi.
An alumna of the school and a former member of the light music club, she does not want people to find out that she was formerly a member of a heavy metal band (Death Devil), thus she covers up by being mild and gentle to her coworkers and especially to students.
She is forced to be the adviser of the light music club, as Ritsu blackmails her after the girls learn of her past.
Though she has a mature and gentle demeanor in the school, Sawako (affectionately addressed as "Sawa-chan" by both Ritsu and Yui) displays a totally different, completely authentic character when she is alone with the light music club. In reality, she is rather wild, lazy and quite an irresponsible teacher who enjoys dressing up the light music club in (sometimes embarrassing) cosplay costumes (like French maid uniforms), much to the dislike of Mio.
She names the club band "Houkago Tea Time" after the members take too long deciding on a name themselves. She once momentarily pitches in for Yui with her Epiphone "1958" Korina Flying V electric guitar (anime only).
She becomes the girls' homeroom teacher in their third year, and puts Nodoka and all the band members (except Azusa, since she is a grade lower) in the same class so she does not have to remember as many names.