When falsely accused, Kyousuke Kamiya lands in Purgatorium Rehabilitation Academy, a place brimming with captivating female students, all with a dark secret of being murderers. To make matters worse, he's infamous as the 'Dozen Demon,' blamed for twelve deaths. Amidst this perilous environment, the enigmatic Renko Hikawa, a voluptuous figure in a gas mask, approaches him, blurring the line between survival and seduction. Can Kyousuke survive this deadly academy and secure his graduation?