A high school graduating class is forced into a sadistic game threatening certain death to all unless they offer one of their own as sacrifice.

It's graduation day. Junichi Shinohara shows up at school following a prolonged absence, to find a gigantic "pit" dug in the middle of the campus and all his classmates gathered in the classroom. Then, a strange message comes over the PA system. "In one hour, everyone will die. There is only one way to survive. You must offer a sacrifice." At first, Shinohara, Rika Suzuki and others think it's some sort of bad joke. But when the first victim is claimed, they realize it's a terrifying reality...

In the final act, the students agonize over their seemingly inevitable fate as they try to figure out why they've been trapped in this gruesome game.

The second act in this sadistic game of life and death unfolds as the desperate student body tries to survive through any means possible.