Mesunie Onna Kyoushi ~Watashi wa Kare no Mae de Hizamazuku~

Female teacher Mizuki is about to get married when she receives confession from her student Akira and turns it down. Akira then involves Mizuki's favorite student Yui to establish physical relationship with her and uses recordered video to blackmail Mizuki. The peaceful days are over for the teacher.

[From vndbreview]