Injuu Gakuen ~La★Blue Girl~

Miko was just an ordinary Japanese teenager attending the prestigious private Himenogi Girls High School. Everything began to change when she witnessed two of her classmates making love to each other. While taking part in various sexual activities, Miko gradually realizes that supernatural demonic forces have taken control of the school.

Based on manga by Toshio Maeda.

[From Moby Games]