Yuuhei

One day, you find a mysterious advertisement claiming, "Will teach you how to sneak into the Hanazono Girls' dormitory."
You call the number on the ad, and a girl from Hanazono High School picks up the phone. She says for 30,000 yens, she'll tell you everything. It's so tempting; you pay the the price and learn how to sneak into the dorm.
"Hanazono Private High School" is a well-known girls' high school that has many beautiful angels. If there were a way to sneak in the dorm, every guy would be delighted to learn how.

Sneaking into the dorm, you learn many things: The girl who walks naked in the woods, the seductive moan you hear every night
Every girl in this dorm is a cutie! Their actions will change depending on what decisions you make. In fact, the dorm is totally outrageous! What's going on!? The fate of these beautiful babes is in your hands!

[Edited from Gamelex]