The Guy She Was Interested in Wasn't a Guy at All, Vol. 1 (manga)

Fashionable and upbeat high schooler Aya falls head over heels for an employee at a local CD shop. He’s got an air of mystery about him, always dressed well, and has impeccable taste in music. Little does she know—this supposedly male employee is actually her female classmate Mitsuki! Mitsuki generally keeps to herself, but since her seat is right next to Aya’s, she can't help but be extremely aware of the other’s crush.

Revealing the truth is out of the question—but perhaps getting closer to Aya wouldn’t be so bad...