Help me!

Kay so I read this Manga a while back, hopefully I can explain it correctly.
So it's a yaoi Manga, about a student and a teacher but when they first met the teacher thought he was a college student. The teacher said they could no longer be in a relationship since they were teacher and student. Later the teacher quits and becomes a university professor, and the student enrolls in the same University. Making their relationship once again professor and student lol.
I think it's something like that. Help please it's one of my faves that I never saved....