Miyu Yamano is the central character of Vampire Princess Miyu, a vampire who appears to be a young girl of about thirteen or fourteen but is in fact much older. She is a half-vampire, born to a human mother and a Shinma father, a race of godlike demons. In the original video animation, her origins are set in post-war Japan, where she lived a normal life until the age of thirteen. At that time, a demon named Larva was sent to kill her. Miyu discovered her vampire nature and instead drank Larva’s blood, sealing his face and voice as punishment and making him her servant. She then learned that her family belonged to a clan of Shinma left on Earth to guard the sleep of ancient beings below. During the transition of guardianship from her mother to her, many Shinma escaped from the darkness, and it became Miyu’s duty to hunt them down and return them to their slumber. To accomplish this, her aging was halted, leaving her ageless. In the television series, her backstory differs: her Shinma father was a guardian killed by an assassin named Tonbi, but not before placing a protective barrier around his daughter. Years later, a traveling theater company of Shinma protectors performed a ceremony to awaken Miyu’s powers. Tonbi killed the protectors and Miyu’s mother, but Miyu herself defeated Tonbi and became the new Guardian.

Miyu’s personality varies between adaptations. In the OVA, she is often depicted as childish, manipulative, and occasionally creepy, taking pleasure in playing with human lives. In the television series, she is more mature, reserved, and introspective, though still morally ambiguous. She is described as amoral—she hunts not only Shinma but also feeds on human blood to survive. She chooses her victims carefully, typically individuals who have suffered a tragic loss. She offers them the chance to be reunited with their lost loved ones in an endless dream state in exchange for their blood. She expresses a deep loneliness and a longing to return to the darkness herself, but she must first banish all the Shinma from Earth and discover her true identity, which has been kept from her since her awakening.

As the Guardian, also referred to as the Watcher, Miyu’s role is to track down and seal away stray Shinma that prey on humans. She possesses several notable abilities that make her a formidable hunter. She is a daywalker, unaffected by sunlight, holy water, crucifixes, or mirrors, and she can cast a reflection. She can teleport, levitate, and open dimensional portals. Her primary offensive power is the ability to summon fire, which burns Shinma and sends them to the darkness. She also carries a flute, which she sometimes uses in her encounters.

Key relationships define Miyu’s story. Her most constant companion is Larva, a Western Shinma who serves her after she drank his blood. Though his face and voice are sealed as punishment, he follows her loyally and fights at her side. Another significant figure is Reiha, a Shinma who becomes a rival and sometimes antagonist. In the manga and expanded material, Miyu also has a complex connection with a human girl named Yuma Koizumi, who vows revenge after Miyu returns her Shinma lover to the darkness. Over the course of the series, Miyu shows subtle development as she grapples with her dual nature, her isolation, and her desire for release from her eternal duty. Her journey is one of balancing her vampiric instincts with her mission as a guardian, all while searching for the truth about herself and her place between the human world and the dark.