Makiko Kisugi is a psychiatrist working at the Prefectural General Hospital in an unnamed Japanese city. She appears as an unremarkable medical professional until she stumbles upon a powerful experimental substance known as the evolution drug, created by the clandestine Towa Organization. The drug had been left behind by a wounded agent named Shinpei Kuroda, who had previously administered it to the dying Nagi Kirima. After witnessing Nagi’s extraordinary recovery and conducting her own animal experiments, Kisugi decides to test the drug on herself. The substance transforms her into a composite human, granting her greatly enhanced physical and mental capabilities, as well as the ability to sense hormones produced by fear. The drug also creates a powerful craving within her for that fear, which she begins to satisfy by terrorizing and eventually murdering her patients. She becomes known as the serial killer Fear Ghoul, preying on strong-willed young women and consuming the fear they emit at the moment of death.

Kisugi’s motivations are initially driven by scientific curiosity and a desire to surpass normal human limits, but the drug’s influence quickly corrupts her into a predator. She continues to experiment on other patients, administering the evolution drug under the guise of treatment, leading to unintended and often tragic outcomes for those she treats. Her actions draw the attention of investigator Nagi Kirima, who eventually tracks the murders back to the hospital. The confrontation between Kisugi and Kirima ends with Kisugi being killed, aided by the entity known as Boogiepop. Though she dies, the evolution drug she spread continues to affect people long after, creating lingering consequences that ripple through the events of the series.

Kisugi is a central antagonist whose ordinary origins contrast sharply with the monstrous role she adopts. Her transformation illustrates the theme of unchecked ambition and the dangerous allure of forbidden knowledge. She has no notable allies, acting alone in her experiments and killings, and her key relationships are defined by conflict: she is opposed by Nagi Kirima and ultimately destroyed by Boogiepop. Her abilities as a composite human make her a formidable opponent, including superhuman strength and speed, heightened senses, and a specific affinity for detecting and feeding on fear.