|Assiah:the realm of humans. Gehenna: the realm of demons.
Normally, these two dimensions would never intersect, but having possessed all material substances, the demons are now intruding on the material world.
But among the human race, there are those who can exorcise such demons - the Exorcists.
During a 3-day drill to prepare Rin and fellow Ex-Wires for actual combat, Amaimon suddenly appears and takes Shiemi as a hostage to lure Rin. Angry Rin fights Amaimon and ends up going berserk! He regains control of himself only to be captured by the current Paladin, Angel, and sent to the Vatican for trial. As the hearing drags on, the Order finds itself unable to decide on Rin's fate, as Mephisto has proclaimed him to be ""a weapon for counterattacking Satan."" Rin is now forced to obey the Vatican's order or face execution!