Love Dissonance (Junnai Dissonance) - Season 1

Masaki Nitta is a high school music teacher who has been appointed as the new homeroom teacher for a class after the previous homeroom teacher's disappearance. Masaki meets Sae Izumi, one of the student from his class, and the two develop a bond with each other through the disappearance case. The two later parted without sharing their true feelings and reunite five years later as a married man and a grown-up woman.