18+ Binetsukko ♭37℃ The Animation

Mutsumi Kagidou finds herself being blackmailed by a perverted student, Inuhiko. The blackmail material? An embarrassing photo of her. In order to get the photo back, she becomes Inuhiko's sex slave and they have all kinds of debauched sex. After a while though, Mustumi tells Inuhiko to forget about the photo since she doesn't mind being his sex slave anymore. And so, a 'unique' relationship is formed between the two of them.

(Source: BakaBT)