Koharu Hondomachi is a petite young woman with short black hair, pink eyes, and a healed injury on the right side of her head, partially hidden by her bangs. She wears a black suit, gray blouse, pink tie, and a floral hair pin. The scar originated from a self-inflicted drill wound during her abduction by serial killer Tamotsu Fukuda—a desperate act to create an id well that exposed his crimes. This trauma reshaped her cognition, amplifying instability and a propensity for reckless behavior.

A police academy graduate recruited into the investigative unit Kura, she operates under Kokuryu Matsuoka. Her talent for reconstructing fragmented visual or conceptual data proved vital in cases like tracking the Perforator, where she defied orders to pursue leads independently. Despite warnings about psychological risks, she fixated on understanding the Mizuhanome system and the fractured mental realms of id wells.

During the Gravedigger case, she killed Haruka Kazuta in self-defense, though her reaction hinted at a darker satisfaction. This prompted Matsuoka to assign her as a Mizuhanome pilot under the alias Miyo Hijiriido, leveraging her ability to navigate unstable psyches. Her dynamic with Fukuda shifted from adversarial to grudgingly respectful over time.

Estranged from her mother, who avoided visiting her post-injury hospitalization, she intertwines personal drives with professional rigor—morbidly fascinated by death and the psychology of killers. Collaborating with Akihito Narihisago’s notes and Fukuda’s insights, she unmasked John Walker, a shadowy manipulator influencing multiple murderers.

Post-trauma behavior reveals erratic impulses, near-suicidal risks, and defiant resolve under pressure. Yet her deductive precision and readiness to confront moral gray areas remain pivotal to Kura’s operations. Physical and psychological scars alike anchor her duality: a sharp investigator tempered by volatile vulnerability.