The main character, Hideo, and his friends are graduating from an orphanage, and have been invited on a graduation trip by Hisui, who is already in society.

Heading up to a lodge in the mountains, they get lost and suddenly find themselves in an abandoned school.

Trapped inside, they can feel a certain poison spread in the air. As the countdown to death begins, a horrifying truth is revealed.

"You will die in 72 hours unless you swallow male semen.
Survive for nine days and you will be released."

Some resist these orders while others give in to their darkest desires──

Bonds break as they struggle between their reason and their instincts.

Will they be able to survive...?

[Roughly translated from DLsite]