Haruka Mikami, a deceased high school student, manifests as a ghost to instigate the central conflict. Her apparition approaches fellow student Asuka Morisaki and other classmates, demanding they locate her scattered body parts within the school premises. This directive arises from her violent death by the supernatural Red Person, which killed her alone at school and dismembered her corpse into eight hidden pieces. Her spectral form reflects this trauma through emotionless, soulless eyes and an overall haunting presence.

Her ghost binds chosen students to a time-loop curse, compelling nightly searches for her remains. Failure to reassemble her entire corpse before dawn traps participants in a repeating cycle: the day resets, and the Red Person hunts and kills them each night. Students killed during the search revive the next morning with intact memories, forced to continue the task. Haruka acts as a catalyst for this recurring curse; when new victims die during the hunt, they replace her as the dismembered corpse requiring assembly, perpetuating the cycle. This pattern extends into sequel narratives, establishing a legacy of victims tasked with identical grim requests.

Before encountering the Red Person, Haruka was an ordinary student with no prior supernatural involvement. The curse's rules prohibit refusing the search and warn of the Red Person's appearance during hunts. Her ghost remains static throughout storylines, showing no development or emotional progression, eternally defined by her unresolved death and the mechanics of the curse she imposes.