Hisae Aoki is a supporting character from the television anime series, where she appears as a classmate of the protagonist, Miyu, and the outgoing Chisato. She is an ordinary high school student whose life becomes intertwined with the supernatural forces that Miyu is sworn to confront.

In terms of personality, Hisae is distinguished by her quiet and introspective nature. She is often characterized as the intellectual of her friend group, with a noticeable love for reading and a thoughtful disposition. Her demeanor is notably shy, contrasting with the more energetic personalities of her peers. This perceptive and scholarly quality leads her to be one of the first in her circle to sense that something unusual surrounds the transfer student Miyu, prompting her to look deeper than surface appearances.

Hisae’s primary role in the narrative is tied to her growing suspicion about Miyu’s true identity. Unlike her friends who accept Miyu at face value, Hisae is driven by curiosity to investigate the strange occurrences that begin to unfold around them. This investigative trait places her at a critical juncture in the early episodes, as she inadvertently edges closer to a hidden and dangerous truth. Her actions serve as a catalyst that brings the human world and the hidden world of Shinma into direct, tragic conflict.

Her key relationships are primarily with her two close friends, Chisato and Yukari. They form a typical schoolgirl trio, with Hisae being the quiet, bookish member who complements the stronger and more cheerful personalities of the others. Her bond with Chisato is particularly significant, as the narrative uses their friendship to highlight the tragic consequences of supernatural interference in human lives.

The character's development is abrupt and tragic, serving as a pivotal moment in the early story. As Hisae’s investigation into Miyu’s secret deepens, she and her friend Yukari make a discovery that places them in grave danger. Shortly after uncovering the truth about Miyu, both are killed by their possessed friend Chisato, who has fallen under the malicious influence of a Shinma named Shidon. This event is a sudden and brutal end to her character arc, where her intelligence and curiosity ultimately lead to a fatal confrontation with forces far beyond human control. Her death functions as a stark illustration of the series' dark tone, demonstrating the lethal consequences of humans prying into the affairs of vampires and demons.

While not possessing supernatural abilities herself, Hisae’s most notable trait is her perceptiveness. She is described as having a keen sense of awareness that allows her to notice the abnormality surrounding Miyu, a sensitivity that her other friends lack. This innate observational skill, though purely human, is what defines her role and ultimately seals her fate.