Kyonyuu Dosukebe Gakuen 1

A famous girl's school one day suddenly became co-ed. This is a school where only the upper echelon of families sent their kids. Most of the girls at this school were far from educated in the ways of sex and lust, they practiced abstinence and scoffed at the thought of boys... except for the four girls in the secret Otome Club. They coerce boys to join and forced them to dress up as girls while they played out all of their sexual fantasies that had been so long suppressed. One unfortunate boy happens to overhear them talking by chance and is found out...