Although the Demon Possession that caused the large-scale power outage was exterminated, the problem remains unresolved as the power shortage in Bayron City continues. Meanwhile, Kisara witnesses a secret meeting between Ayano and a mysterious man. To confirm Shu's feelings, she uploads a photo of the scene to social media. Successfully lured by Kisara, Shu rushes Ayano and the mysterious man – an Anti-Demon Bureau detective named Tetsuya Mikami – and, in an unexpected flow of events, realizes that Ayano was hiding her intentions and planning behind his back. An unparalleled sense of tension lofted between the two.

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...

In the middle of the battle against the demons on the artificial island, Kisara was stabbed by a spear before Shu's eyes. Saved by Ayano and Sharon, Shu helplessly evacuates from the fight when he sees the person he's been looking for—his younger sister, Kanna. Then, humanity's desperate resistance, backed by the focused efforts of Bayron City, proves futile as the extent of the large-scale disasters caused by Kanna, now certified as an S-Class demon, expand. Kisara collapsed due to her injuries and lost consciousness as her vitals disappeared. Unable to move, Shu just stares at her. And as if responding to his heart, Kisara gently awakens.