Kiki Asukai is a young woman with long black hair and green eyes. She was initially seen in an oversized pale yellow jumper and blue skirt, later forced into a white bodysuit patterned with circuitry after her abduction. Growing up in Fukui Prefecture, she rarely attended elementary or middle school, leading to expulsion from boarding school. When her parents refused her return, she was institutionalized. At 18, she attempted suicide and was hospitalized, later pursuing art. Three further suicide attempts resulted in repeated hospitalizations. At 21, she became the final victim of serial killer Denshin Katsuyama ("The Challenger"); detective Funetaro Momoki rescued her while Akihito Narihisago killed Katsuyama. Returning to the hospital, she vanished three months later, coinciding with a mass coma incident involving 13 nurses. Three nurses later awoke reporting identical disturbing dreams.

Momoki's reports describe her as quiet, intelligent, gentle, and friendly, with chronic suicidality and resignation toward death. She expressed a fear that her body would disintegrate and merge with reality, distorting the world's structure. This fear arose from uncontrollable psychic abilities: involuntarily projecting her thoughts, memories, dreams, and imaginations into others' minds. Her dreams consistently featured brutal murders by various serial killers, starting with John Walker, who later invited other killers into her dreams. These experiences caused her to feel she was "losing herself" in a violent world.

Her powers became central to the Mizuhanome System's functionality. John Walker (later revealed as Takuhiko Hayaseura) orchestrated her kidnapping to exploit her abilities as the system's core. Her telepathy enabled the creation and navigation of "id wells," digital representations of serial killers' unconscious minds. Within these wells, she manifested as "Kaeru," a recurring murder victim whose varying death methods provided investigative clues. This connection stemmed from her nightmares being absorbed into the system, making her the literal catalyst for well-diving technology. Her physical health deteriorated significantly while linked to the Mizuhanome, leading her to beg Narihisago to end her life during his investigation within her id well—a request he refused.

Hayaseura ultimately released her from containment, triggering widespread unconsciousness as her powers transported individuals into overlapping id wells. To contain the crisis, Momoki used a prototype Mizuhanome suit to safely reach her and reintegrate her into the system, stabilizing her influence. This ended the chaos but left serial killers Tamotsu Fukuda and Nahoshi Inami in permanent comas after their consciousnesses were destroyed within the wells. Her ultimate fate sees her remaining confined within the Mizuhanome, with the hope that future technology might suppress or free her from her powers.