Read manga: Ijimeru Aitsu Ga Waruinoka, Ijimerareta Boku Ga Waruinoka?

manga
Summary:

Aizawa was bullied by Suzuki to the point of becoming truant. He picks himself back up and becomes a teacher. 20 years later, his bully's daughter is one of his students and she's being harassed in class, a secret she keeps from her father.