The Guy She Was Interested In Wasn't a Guy at All, Vol. 2 by Sumiko Arai

Aya’s found out that the guy she was interested in isn’t a guy at all—and she’s also realized that she just can’t keep her cool around Mitsuki! The two haven’t quite put a name on their complex, earnest feelings, but they only grow as the pair continues to bond over the music they love. With their senior year at hand, future plans are coming into question…and Aya’s thrown for a loop when a mysterious woman shows up and wants Mitsuki to go overseas!