Ryuudouji Shimon no Inbou

Ryuudouji Shimon no Inbou – A school secretly trains its students to be sex slaves who are then sold to the highest bidder. Ryuu, a male teacher, is entrusted with training the students. The head mistress, Sayaka, promises him a reward at the end if he does a good job. Spoiler alert: He does a good job.