Yuuko Tachikawa

Yuuko is observant, thoughtful and courageous, but her confidence in reasoning with other people can make her underestimate threats that do not think like humans.

She pays close attention to Hideo after becoming interested in drawing him and notices inconsistencies in his appearance. Information from her brother gives those observations a frightening possible explanation.

Even after suspecting the truth, Yuuko initially prefers communication to immediately reporting Hideo. She hopes that if he is intelligent enough to live as a student, he may also be capable of understanding why killing humans is wrong.

Yuuko is an ordinary human without supernatural abilities.

She has artistic skill and a strong eye for visual details. This observational ability contributes to her suspicion of Hideo Shimada.

Yuuko also prepares a chemical defense before confronting Hideo, demonstrating foresight despite having no realistic physical means of fighting a Parasite directly.

Yuuko attends school with Shinichi Izumi, Satomi Murano and Akiho Suzuki.

After learning from Haruki Tachikawa that creatures capable of disguising themselves as humans exist, she begins connecting that information to the abnormalities she has noticed in Hideo.

Yuuko confronts Hideo privately and tests him after becoming convinced that he is one of the creatures. When Hideo transforms and attacks, she throws paint thinner onto him. The chemical disrupts the coordination of his Parasite cells, causing uncontrolled transformations that lead directly into the school massacre.

Yuuko survives the encounter by escaping through a window and is hospitalized afterward. Her testimony helps expose the existence of the creature responsible for the attack.

Haruki Tachikawa is Yuuko's older brother. Information he shares about the police investigation gives her the knowledge needed to recognize the danger surrounding Hideo.

Satomi Murano is one of Yuuko's close friends at school.

Akiho Suzuki is another member of Yuuko's friendship group.

Shinichi Izumi is Yuuko's classmate and already knows the truth about Hideo.

Hideo Shimada becomes the focus of Yuuko's suspicions. Her attempt to confront him exposes his true nature and triggers the loss of control that precedes his rampage.