18+ Mesu Kyoushi 2: Injuu no Rasen

Shingo is a high school student. He likes to peek at female students changing their clothes. One day, Sanae, a training teacher, comes to his school. He immediately tries to peek at her, but he has an accident and is taken to a sickroom. Rihoko, a medical doctor, secretly gives him a drug. With the drug, he plans to train his teachers and classmates to become his sex slaves.

(Source: ErogeShop)