Hisae Aoki is a supporting character from the anime television series Vampire Princess Miyu. She is a classmate of the series' protagonist, Miyu, and her friends Chisato Inoue and Yukari Kashima. Hisae is a young girl of school age with a short, slight build, brown hair, and glasses, which complement her reserved and studious demeanor. Often described as shy and quiet, she is the most intellectually inclined member of her friend group. Hisae is known for her love of reading and is considered one of the top students at her school, characteristics that mark her as a bookworm among her peers.

Hisae's primary role in the story is as a member of the small circle of human friends that the vampire princess Miyu attempts to blend in with while posing as an ordinary schoolgirl. Unlike the more outgoing and impulsive Chisato, Hisae is observant and perceptive, a trait that ultimately defines her narrative purpose. Her intelligence and keen nature lead her to sense that something unusual or strange surrounds the quiet transfer student, Miyu. This growing suspicion drives her to begin investigating Miyu in an attempt to uncover the truth behind her enigmatic classmate. Her motivation stems from a natural curiosity and a desire to understand the inexplicable, rather than from malice.

The pursuit of this truth becomes Hisae's fatal flaw. Her investigation leads her and her friend Yukari to discover the true nature of Miyu as a vampire princess. However, before they can act on this revelation or fully comprehend the danger of the supernatural world they have stumbled into, they are confronted by Chisato. In a tragic turn, Chisato, who is secretly a shinma, or demon, kills both Hisae and Yukari to prevent them from exposing Miyu. Hisae's death is a pivotal moment that underscores the series' themes of tragic fate and the inevitable sorrow that surrounds Miyu's immortal existence, demonstrating how even well-intentioned curiosity can lead to devastating consequences when it crosses into the realm of the supernatural.

Hisae's key relationships are confined to her life as a schoolgirl. She is a loyal friend to Chisato and Yukari, forming the trio that befriends Miyu at the start of the series. Her bond with Chisato is particularly significant, as it is Chisato who most directly welcomes Miyu into their group, which Hisae quietly accepts. The development of her character is therefore brief but complete; she transitions from a background presence as a quiet, intelligent student to an active, if doomed, investigator whose suspicions set the stage for her own demise. Hisae does not possess any notable supernatural abilities or combat skills, her strengths being entirely intellectual and academic, which ultimately proves insufficient to protect her in the dangerous world of the shinma.