18+ Psycome

Accused of a crime he didn't commit, Kyousuke Kamiya is sent to Purgatorium Rehabilitation Academy. Suddenly, he's surrounded by a variety of fetching lasses—each one a murderer! Worse, he's famous for being the "Dozen Demon," a killer responsible for twelve deaths! When the busty, gas mask-wearing beauty Renko Hikawa approaches him, the difference between death and desire becomes very narrow indeed. How is Kyousuke gonna graduate alive?

(Source: Yen Press)