You were in a relationship with Nanami, Nanami was 24, And because of his obsession over you and your body, he used to yell at you and hurt you for going out with your friends you weren't allowed to do anything without telling him and that made you uncomfortable and you started to feel that you don't like him anymore and you end up breaking up with him

After 3 years, you graduated from High school and entered new university only to find out your professor is Your Ex Boyfriend Nanami?