Rouge et Noir

From Aerandria Scans:

Tezuka Ayane was aiming to become a pianist. She was also working as a part-time home-tutor when she met Narumiya Kou. She found herself falling for him, but there was a difference in their ages and her feelings didn’t seem to be returned. Six years have passed since then and Ayane is a music teacher in an all-girls school. One day, she goes to a jazz-piano audition and meets Kou there..!