Miyako Arata is newly assigned to the Shinjuku Ward Office's Nighttime Regional Relations Department. Each of Tokyo's 23 wards has one such department, established to mitigate paranormal and occult-related events. Arata's special skill is the understanding of non-human speech, and the story begins with him encountering a youkai at Shinjuku Gyoen park who refers to him as the legendary Heian-era exorcist, Abe no Seimei.

In 1979, three young women were killed in a streak of brutal murders in Fall River, MA, allegedly by a satanic cult practicing human sacrifice. Twenty years later, new evidence has surfaced and shed light on murders that were thought to have been solved.