Makiko Kisugi is a psychiatrist who works at the Prefectural General Hospital. Before the events of the series, she witnesses the remarkable recovery of a patient named Nagi Kirima, who had been treated with an experimental evolution drug developed by the Towa Organization. After the drug is left behind by a fleeing agent, Kisugi discovers it and begins her own experimentation, first on rats and then on herself. She uses the drug on her own body, transforming into a composite human. The drug grants her vastly enhanced physical and mental abilities, as well as the power to sense the hormones that produce fear in others. This ability creates a craving for fear, which she begins to consume by terrorizing her patients and eventually murdering strong-willed girls. She becomes known as the serial killer Fear Ghoul.

Kisugi’s personality before the drug is described as completely ordinary. After taking the evolution drug, her nature twists dramatically. She develops a desire to prey on the weaknesses of particularly courageous people, doing so to comfort her own former cowardice. She becomes cunning and predatory, using her position as a doctor to identify and target vulnerable individuals. Her primary motivation is the consumption of fear itself, which she finds addictive. She also gives the drug to some of her patients under the guise of healing, which worsens their conditions and triggers their own evolution.

In the narrative of Boogiepop Phantom, Kisugi serves as a key antagonist whose past actions set the stage for many of the strange events in the city. Her distribution of the evolution drug creates several of the evolved individuals who appear throughout the series. She is ultimately confronted by Nagi Kirima, who has been investigating the serial killings. During their battle, Kisugi initially overpowers Kirima, but she is eventually killed with the help of the entity known as Boogiepop. Her actions also lead to the continued evolution of other characters who come into contact with the drug’s lingering effects.

Kisugi’s primary relationship is as an adversary to Nagi Kirima, the fire witch who tracks her down. She also indirectly connects to Touka Miyashita and the Boogiepop persona through the chain of events her crimes set in motion. Her development follows a trajectory from an unremarkable medical professional into a monstrous predator, then to her eventual defeat. Her notable abilities include superhuman regeneration, enhanced combat capability, the capacity to sense fear, and the ability to perceive an opponent’s psychological weaknesses. Because she is a composite human, she also possesses heightened physical and mental attributes beyond normal human limits.