The Celestial Abbey — — Publicly seen as advocates for philanthropy, they are the world's largest Exorcist group. The identity of the mysterious nun who suddenly appeared in Bayron City is one of the most dangerous persons in the Celestial Abbey, Sharon Holygrail. Known as "Sharon the Chaste," she is one of the 12 remarkable Exorcists called "Living Relic." The Anti-Demon Bureau faces a growing sense of danger with the emergence of a new power that could shake the framework of their organization. Meanwhile, as Shu is injured and sleeping, Kisara tells Ayano about the events atop the snowy mountain that led to the intertwined fate of her, Shu and Sharon.

Thanks to Shu and Kisara's efforts, the Anti-Demon Bureau successfully detained Sharon, and peace returned anew to Bayron City. With his companions Mikami and Miles, Shu once again pursues the truth behind the continuous D Hazards that have been manipulated by some entity's volition. They continue compiling deductions to pin down the identity of the "True Agent," who they presume is lurking behind Junya Hanamura, the murdered Demon Agent. At the pinnacle of their deductions, Mikami reaches a certain conclusion and tries to contact Shu in a hurry...