Chihiro Chimatsuri serves as the school nurse at Seijumonji High School and directs the Chimatsuri Blood Research Institute. She possesses short red hair and deep blue eyes. Her attire typically consists of a revealing red latex dress with a zipper, a white lab coat, a black choker, and red slipper shoes.

Characterized by immorality and a taste for excitement derived from trouble and confusion, she often uses vulgar speech, yet possesses an underlying kind-hearted nature. A persistent interest in acquiring and studying the blood of the vampire Mai Vlad Transylvania drives her involvement in supporting Mitsugu Bamba's efforts to provide blood for Mai.

To facilitate her goals, she establishes and advises the school's Blood Donation Club. While the club officially collects blood for Mai, she simultaneously uses it to pursue personal research into rare blood types. Her methods frequently involve unethical practices, including drugging students and performing non-consensual procedures. Notably, she drugs Mai to conduct hypnotherapy, forcibly extracting traumatic memories against Mai's will. This action reveals critical aspects of Mai's past, including her family's persecution and the death of her human friend.

She also plays a role in establishing a night school at Seijumonji High to accommodate Mai and others, further integrating herself into their activities. Her backstory includes a treasured vial of blood labeled "Memories," whose origin involves a story about a young girl and boy experiencing a dramatic adolescence. The etymology of her name reflects her association with blood: "Chihiro" combines characters meaning "blood," "ratio," and "spine," while "Chimatsuri" means "blood festival" or "blood ritual."