Blue Exorcist manga volume 31 features story and art by Kazue Kato.

The Knights of the True Cross begin their attack on Satan's fortress in a coordinated assault. The lord of demons summons the powerful Asmodeus, the King of Lust, who relishes the chance to take on Shura. Osceola squares off with Amon, who doesn't think much of the exorcists' efforts. The battle provides an opportunity for Rin and Yukio to breach the gate, but getting through it is no easy task. With Shura and Osceola barely hanging on, desperate measures will be required…