Haru Nanakusa is a vampire who is already deceased by the time the main events of the story take place, yet her history and relationships are central to understanding several key characters. She is the biological mother of Nazuna Nanakusa and the vampire who turned Kabura Honda into her kin. Her appearance is nearly identical to her daughter's, with the most notable difference being that her hair is longer than Nazuna's. She is often depicted with a cigarette, a habit that contributes to her mature atmosphere.

During her human life, Haru worked as a nurse at a hospital. It was in this professional setting that she first met Kabura Honda, a meeting that would eventually lead to Kabura becoming her vampire follower. Her background in healthcare reflects a personality described as composed, caring, and nurturing, showing gentleness both as a human and after becoming a vampire. Despite her supernatural nature, she retained a strong sense of responsibility and care for those around her.

After becoming a vampire, Haru formed a partnership with another vampire named Kiku Hoshimi, as the two of them searched for a way to become human again. This search for a return to humanity was a significant motivation for her, driven by a longing for the life she had lost. Her quest for a cure for vampirism highlights a deep-seated desire for redemption and a refusal to completely abandon her human side.

Haru's most important relationship is with her daughter, Nazuna. The story reveals that Nazuna was a naturally born vampire, a rarity born from the union of Haru, who was already a vampire, and a human man whom Haru loved. Haru chose to marry this man without turning him into a vampire. Against expectation, she was able to conceive and give birth to Nazuna. However, for the sake of her human husband, Haru refrained from drinking enough blood, which left her in a weakened physical state. She died a few years after Nazuna's birth. Before her death, she entrusted the care of her young daughter to Kabura.

Haru's legacy deeply influences the plot. Her past actions, especially her desire to regain her humanity in collaboration with Kiku, set important narrative threads in motion. Her caring influence and tragic backstory continue to affect Kabura and cast a long shadow over Nazuna's personal journey. Information about notable supernatural abilities beyond standard vampire traits is not available, but her significance lies in her emotional impact and the revelations about Nazuna's unique origin as a child born to a vampire and a human.