Maria, also known by her full name Ai Imari, is a mysterious woman who serves as a researcher and the leader of a group investigating the Pupa virus. She possesses extensive knowledge about the virus and conducts experiments related to it. Her research has led her to develop a cold and detached perspective on human life, and she speaks her mind without hesitation, even in serious situations. She is often seen carrying her pet cat, Seto.

In appearance, Maria is an adult woman with very long black hair that reaches past her hips, red eyes, and conspicuous scars on her body. She typically wears a black dress that resembles a mourning gown, along with a hat, pumps, tights, and detached sleeves.

Her role in the story is primarily as an antagonist figure who manipulates events behind the scenes. She is responsible for uncovering one of two ancient immortal monsters that had been kept in larval form, which she then experimented on for thirty years. The mate of that monster escaped and was later reborn as Yume Hasegawa, losing all memories of its past. Maria’s actions and experiments are central to the unfolding horror involving the siblings Utsutsu and Yume.

Maria’s motivations are driven by her scientific curiosity and a lack of empathy for the subjects of her experiments. She does not hesitate to use others for her research and treats the Pupa virus as a phenomenon to be studied rather than a threat to be contained. Her relationships are largely transactional; she interacts with the main characters as test subjects or obstacles, and she shows little personal attachment beyond her cat.

There is no notable character development shown for Maria within the available information. She remains a static figure driven by her cold research goals. Her notable abilities are rooted in her scientific expertise and her long-term experimentation with the Pupa virus, giving her an understanding of its nature that exceeds that of other characters. She also has access to resources and facilities for her work.