A rumor had spread in the girls high school. You will be caught by the devil if being in classroom alone after school.....
But it is not just a rumor! The Devil does exist!!
Girls who met the devil were put under a spell and the only way out is to have sex with someone...

(modified from DLsite http://www.dlsite.com/ecchi-eng/work/=/product_id/RE016473.html)