Nazuna Nanakusa is the female protagonist of Call of the Night, a vampire born rather than turned. Her mother, Haru Nanakusa, was a vampire and her father was human, making her a rare hybrid. Haru died shortly after giving birth, and Nazuna was raised by Kabura Honda, an older vampire who acted as a foster mother. Nazuna attended a night school where she befriended Kyouko Mejiro, a classmate whose life would later be shaped by tragic circumstances. Nazuna has remained physically small since early childhood, appearing youthful despite being approximately forty years old. She lives alone in a sparsely furnished apartment in Komori, sustaining herself by running a snooze shop where she helps insomniacs fall asleep and drinks their blood, later also working at the Vamp Maid Cafe for the salary and after-work beer.

Nazuna's personality is laid-back, sarcastic, and mischievous. She speaks openly about sexual topics and enjoys teasing others with dirty jokes, yet she becomes flustered and uncomfortable when genuine romantic love is mentioned. This contradiction defines her emotional core: she is bold and confident in casual interactions but deeply avoidant of intimacy and commitment. She fears emotional vulnerability, likely stemming from her mother's death and her solitary upbringing. She loves playing video games, drinking beer, and exploring the city at night. She is not well-versed in modern technology, owning retro gaming consoles and an old flip phone rather than a smartphone.

Her motivations shift over the course of the story. Initially, she approaches life with carefree detachment, seeking amusement and sustenance without forming lasting connections. When she meets Kou Yamori, a middle school boy wandering the night, she finds his blood exceptionally delicious and agrees to let him keep her company in exchange for feeding on him. Kou expresses a desire to become a vampire, which requires him to fall in love with Nazuna. Though discomforted by the prospect of love, she agrees to this arrangement. As their nightly encounters continue, Nazuna develops genuine feelings for Kou, though she struggles to admit or act on them. Her primary motivation evolves from self-indulgence to protecting those she cares about, particularly Kou, and confronting the emotional wounds of her past.

In the story, Nazuna serves as the catalyst for Kou's journey and the embodiment of the series' themes of nighttime freedom and self-discovery. She introduces him to the nocturnal world and its inhabitants, challenging his perceptions of life and happiness. Her role deepens as she faces her own unresolved history. When her former friend Kyouko Mejiro reenters her life as a vampire hunter named Anko Uguisu, Nazuna is forced to confront guilt and betrayal from their shared past. She ultimately chooses not to kill Kyouko and helps her find peace. Later, after Kou's unexpected transformation into a half-vampire hybrid, Nazuna protects and supports him despite her unease with his altered state. She accompanies him on a school trip to Hokkaido to reconcile with a friend, where Kou is nearly killed by the vampire Kiku Hoshimi. These events strain their relationship, forcing both to reevaluate what they mean to each other.

Key relationships include Kou Yamori, who becomes her closest companion and romantic interest; Kyouko Mejiro, her former friend whose tragic fate haunts her; and Kabura Honda, her caretaker who remains a distant but concerned presence in her life. Nazuna also interacts with other vampires such as Seri and Nico Hirata, maintaining a generally independent and sarcastic demeanor.

Notable abilities stem from her nature as a born vampire. She possesses superhuman strength capable of destroying concrete, speed that exceeds human perception, and regeneration that allows her to recover from gunshot wounds or lost limbs. She can phase through solid matter with concentration, leap across buildings in a way that resembles flight, and manipulate memories through blood consumption. She also has a supernatural charm effect that draws people to her. Despite her immense potential, Nazuna rarely trains or takes her powers seriously, relying on raw talent rather than refined skill. This laziness means that older, more disciplined vampires can sometimes overpower her, but she remains one of the most powerful characters due to her inherited abilities. Her weaknesses include an aversion to romance and a tendency to avoid emotional confrontation, which hinders her personal growth and complicates her relationship with Kou.

Throughout the narrative, Nazuna develops from a carefree loner into a loyal and protective figure who learns to open her heart to others. Her journey involves reconciling with her past, accepting her feelings for Kou, and finding meaning beyond mere survival and amusement. She remains a complex blend of chaotic energy and tender vulnerability, embodying the nocturnal world she inhabits.