18+ Kagai Jugyou: Shiritsu Hakurei Joshi Gakuen

The protagonist is going to be a teacher at the prestigious girl school, because he is forced into an arrange marriage with the headmaster's daughter by his father. While disagreeing, in order to achieve his goal, he accepts the engagement. His aim is to train the girls whom he takes interested in and turn them into sex slaves, staring with his own fiancée.

(Source: Official site)