After his confrontation in the Nether with his younger brother Shou, Shinra Kusakabe's resolve to become a hero that saves lives from the flame terror strengthens. Finding a way to turn the Infernals back into people, unraveling the mystery of the Evangelist and Adolla Burst, and saving his mother and Shou—these are the goals Shinra has in mind. However, he has come to realize that attaining these goals will not be easy, especially with the imminent danger the Evangelist poses.

The Evangelist's plan is clear: to gather the eight pillars—the individuals who possess Adolla Burst—and sacrifice them to recreate the Great Cataclysm from 250 years ago. Having been revealed by the First Pillar that the birth of a new pillar is approaching, Shinra is determined to protect his fellow pillars from the Evangelist. Thus, the fiery battle between the Special Fire Force and the Evangelist ignites. Together with the Special Fire Force, Shinra's fight continues as he uncovers the truth about the Great Cataclysm and the nature of Adolla Bursts, as well as the mysteries behind human combustion.

Kazuya Kinoshita is a 20-year-old college student who has a wonderful girlfriend: the bright and sunny Mami Nanami. But suddenly, he doesn't. Without warning, Mami breaks up with him, leaving him utterly heartbroken and lonely. Seeking to soothe the pain, he hires a rental girlfriend through an online app. His partner is Chizuru Mizuhara, who through her unparalleled beauty and cute demeanor, manages to gain Kazuya's affection.

But after reading similar experiences other customers had had with Chizuru, Kazuya believes her warm smile and caring personality were all just an act to toy with his heart, and he rates her poorly. Aggravated, Chizuru lambastes him for his shameless hypocrisy, revealing her true pert and hot-tempered self. This one-sided exchange is cut short, however, when Kazuya finds out that his grandmother has collapsed.

They dash toward the hospital and find Kazuya's grandmother already in good condition. Baffled by Chizuru's presence, she asks who this girl might be. On impulse, Kazuya promptly declares that they are lovers, forcing Chizuru to play the part. But with Kazuya still hung up on his previous relationship with Mami, how long can this difficult client and reluctant rental girlfriend keep up their act?