Kurumi Imari is the main character's childhood friend and neighbor, attending the same academy and serving as president of the school's art club. She maintains a daily routine of waking him each morning, demonstrating concern through their interactions, including preparing meals despite a limited cooking repertoire focused primarily on curry dishes. Her feelings for him extend beyond friendship, though initially unreciprocated.

Trained in Shorinji Kempo and holding a black belt, she possesses significant martial prowess used defensively. Her life becomes entangled in supernatural conflicts after encountering a dark magic artifact. Her status as one of the school's few virgins designates her as the ideal sacrifice for a ritual orchestrated by the primary antagonist seeking a vessel for reincarnation, leading to her capture and physical assault intended to break her spirit before the ceremony.

During the climactic confrontation, the antagonist successfully transfers her consciousness into Kurumi's body through occult means. However, this possession proves incomplete; Kurumi's soul persists alongside the invading presence rather than being fully displaced, creating an unresolved spiritual conflict.

Years later, she resurfaces as a psychic investigator leading murder cases, having matured physically with more pronounced feminine features. This professional path connects directly to her traumatic past, as the investigations inadvertently reawaken the dormant antagonist consciousness within her, triggering internal battles for control during inquiries. Her work receives guidance from a former instructor now operating within religious circles. The lingering antagonist presence within her psyche continues to influence events, driving central conflicts throughout her adult investigations despite her efforts to maintain autonomy.