Sawako is a music teacher who is the adviser for the wind instrument club at the girls' school. An alumna of the school and a member of the light music club in her student days, she does not want people to find out that she was formerly a member of a speed metal band called Death Devil (of which she was both lead guitar and vocalist and went by the stage name of "Catherine"), 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. However, she is able to juggle being the adviser for the wind instrument club as well, even as the story progresses. 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 is quite an irresponsible teacher who enjoys dressing up the light music club in (sometimes embarrassing) cosplay costumes (like French maid uniforms), much to the dismay of Mio. She gets a thrill out of the rare moments where she is praised for her work.
She names the club band "Ho-kago Tea Time" after the members take too long deciding on a name themselves. In the anime, she once pitches in for Yui with her white Epiphone "1958" Korina Flying V electric guitar. 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. An episode in the second anime season reveals that she owned one of the first Gibson SG models (from around 1960 with a custom stoptail bridge) which is later sold. Due to her relation to the club members, the other students in her class start to call her Sawa-chan as well, ruining her image as a mild-mannered teacher. Her image is further ruined after Death Devil is temporarily reunited at a wedding reception for a high school alumnus. Regardless, her popularity with the students remains unchanged. In spite of her laziness, she still proves herself to be an able mentor, as shown by her willingness to coach Yui as the lead singer and attending their performances. Her music abilities apparently have not dulled over the years, as she is able to substitute for Yui at the school festival at almost no notice without the assistance of a music score, even without any prior practicing of the band's song. Sawako is also very perceptive: she immediately sees through Ui's disguise when she impersonates her sister and on several occasions boasts to the club that there is nothing she cannot see.