Sawako Yamanaka is a teacher at Sakura High. She is 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.
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 "After-School 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 (anime only).
She becomes the girls' homeroom teacher in their third year, and puts Nodoka and all the band members (except Asuza, since she is a grade lower) in the same class so she does not have to remember as many names.
The Light Music Club members are approaching their graduation from high school, so they decide to go on a band trip to the United Kingdom.