Nazuna Nanakusa is an elegant yet below-average height natural-born vampire who stands at a short, petite build similar to a middle schooler. She has notably pale skin, sharp fangs, azure-colored eyes with unique target-like rings, and long, pale purple hair styled into distinct twin-ring braids on the sides of her head. Her signature outfit consists of an oversized, hooded black cloak worn over a deeply cropped black leather keyhole top, short denim shorts, and thigh-high wedge boots. Personality-wise, she is exceptionally carefree, lazy, and relaxed, frequently making bold or dirty jokes to tease those around her. Ironically, despite her uninhibited behavior, she becomes intensely pure-hearted, shy, and flustered whenever genuine romance or love is brought up. As a creature of the night, she spends her late hours wandering neon-lit urban streets, playing video games, and drinking beer. To sustain herself without being a villain, she operates a cozy nocturnal sleep shop where she provides professional massages to human clients in exchange for drinking their blood while they drift off.

Kou Yamori is a middle school student who stands at a relatively short and slender height of 5 feet 1 inch (155 cm). He possesses messy, slightly spiky black hair, distinctive eyes with small pupils and heavy bags under them from his chronic lack of sleep. His typical casual outfit consists of a simple white t-shirt layered under a loose, open black hoodie paired with dark pants. Personality-wise, Kou is highly analytical, detached, and blunt, often struggling to understand normal human social cues or typical romantic attraction. Ironically, despite being popular with girls due to his naturally polite, honor-student facade, he secretly feels like an outcast who does not fit into everyday society. To escape the suffocating nature of his daily routine, he sneaks out past midnight to wander the lonely, neon-lit city streets in search of purpose. It is during these late hours that he acts as an assistant to a private detective and spends his time with Nazuna, desperately trying to fall in love with her so he can permanently transform into a vampire.

Akira Asai is a middle school student who stands at a average height of approximately 5 feet 2 inches (158 cm), making her just slightly taller than Kou. She has a neat, studious appearance with straight, shoulder-length brown hair, soft brown eyes, and is most frequently seen wearing her neat school uniform or a modest track jacket. Personality-wise, she is serious, responsible, and a straight-A honor student who acts as the grounded voice of reason in the group. Despite her mature and logical facade, she deeply cares for her childhood friends and struggles with a profound sense of loneliness. She is deeply attached to Kou and frequently sneaks out in the dead of night to wander the streets just to ensure he is safe. Upon discovering the supernatural world, she becomes a close ally to both Kou and Nazuna, acting as a bridge between the regular human world and the nightlife. Her presence adds great dramatic tension because she hates the dangerous nature of vampires but respects Kou's ultimate dream to become one.

Anko Uguisu, Kyoko Mejiro is a 28-year-old private detective who secretly operates as a highly accomplished vampire hunter. Her weary, disheveled appearance features messy brown hair, tired eyes framed by glasses, a striking turtleneck, and a signature beige trench coat. She wanders the nocturnal underworld as a heavy chain-smoker with a low tolerance for alcohol, often carrying a hidden handgun and a butterfly knife. Professionally, she investigates missing person cases involving supernatural elements, tracking down targets by exploiting the personal and emotional items tied to their human pasts. Driven by intense trauma after her father transformed into a vampire and slaughtered her family, she harbors a deep vendetta and initially views all vampires as irredeemable predators. Personality-wise, she is analytical, fiercely intelligent, and blunt, carrying a cynical outlook that masks her inner grief and psychological scars. Despite her unstable, cold, and borderline psychopathic streak during combat, she has a supportive, vulnerable side that allows her to eventually bond with Kou and Nazuna.