Sakai, Wakana

Wakana is known for being somewhat of a loner, and that is due to her outward personality that may seem harsh to others. She is skilled at playing the piano and has a cat as a pet. Despite the fact that she is very good at singing, she refuses to do so to the point of turning down Konatsu's attempt to recruit her into her new choir club. Before joining Konatsu's choir club, she never went out or did any extracurricular activities with her classmates.

[Spoiler] Initially, Wakana refuses to join Konatsu's new Choir Club, but with the help of Sawa, she agrees to do so. Her mother died when she was in her last year of middle school and hid her sickness from her to have Wakana focus on her entrance exams, but then she started living in regret for not being able to properly bid farewell to her. When her father shows Wakana her mother' notes regarding a song she was composing to her, she finally manages to move forward and join the club as a regular member while dedicating herself to finish her mother's song. [/Spoiler]

References: Character Book, events in anime