A small port town called Fuugan, surrounded by deep mountains in the Tohoku region. It was a quiet rural area with no major industries or tourist attractions to speak of. The only notable building was the prison at the foot of the mountain. In this backwater town, illegal human experiments were being planned, away from prying eyes. However, trouble struck just before the experiments were set to begin, and Fuugan was devastated overnight.

And then, prisoner Okamatsu Daigo woke up as usual.

[Translated from the official site]