Help me find a manga

It’s not a recent one, I think I was reading it in 2014-2016, can’t remember the exact year. So it was a Japanese yaoi manga with mature content about 45+ years old teacher (probably hight school) portrayed as a loser with untidy looks and a smoker. ML is younger new employee who has recently started working at this school, has a reputation of an upstanding teacher, wear glasses and a black turtleneck. The story goes around ML sexually assaulting the older teacher, humiliating him and blackmailing. They continue have this twisted relationship until the MC develops feelings toward the younger teacher.

The cover for this manga features MC sitting on a chair backwards and leaning his head on his hand with tired look and unshaven face.