Blue Exorcist manga volume 30 features story and art by Kazue Kato.

Exhausted by the effort to contain Satan, Shemihaza has transferred her role - to Shiemi! Rin and the other Exwires are stunned to see Shiemi again, and old friends reunite. But although the ritual to seal Satan was completed, the demon lord transformed in order to survive. Now, his immense form is part of the earth itself, with his heart protected in the center of a vast fortress! The Exorcists and Exwires of the Knights of the True Cross regroup and ready themselves for a renewed assault on Satan's stronghold, but this time, the forces of the Illuminati will also be defending their father…