The "elite student in music room 2" turns out to be Haruki's delinquent classmate, Kazusa Touma.  With his characteristic pushiness, he tries to get her to join the light music club.  But his pushiness backfires, and only makes her more annoyed.  Setsuna gets irritated... no, involved, and approaches Kazusa secretly.
That's what makes you who you are.
Das macht dich zu der Person,
die du bist.
Eso te hace quien eres.
Así es como tú eres.
Essa é a sua identidade.