Seri Kikiyou sports blonde hair with brown roots, golden eyes, and pink lips. Her kogyaru-inspired look features a modified school uniform: a white t-shirt, sandy brown sweater, dark blue skirt shortened at the hem, black socks, brown loafers, and sometimes loose socks. A visible purple bra beneath her shirt, a tiny chain necklace, and four piercings on her left ear complete her distinctive style. She embodies a carefree and flirtatious personality, confidently revealing her cleavage when noticed. Seri actively chases trends, expressing surprise when others miss popular songs, and generally scorns retro things. Despite this lightness, she casually threatens to kill humans, rationalizing it as natural vampire behavior. These threats, like the one against the obsessive Akihito Akiyama, often remain unfulfilled. She admits emotional fatigue, finding flirting unexciting and lamenting that servant candidates become possessive and annoying, forcing her to cut ties. Hypocrisy surfaces as she advocates against human-vampire friendships while desiring a platonic bond with Akihito. Her inexperience with non-romantic connections complicates this, leading to tearful reluctance to end things. Relationships shape her story. Initial encounters with Kou Yamori involve near-blood-sucking and attempts on his life to protect vampire secrecy. They later form a sympathetic rapport, sharing worries and singing karaoke. She gifts him a piercing and offers dating advice, yet attacks him when he defends Akihito. Her dynamic with Akihito starts after his romantic rejection; she relates to his disinterest but inadvertently sparks his obsession through flirtation, causing estrangement. Reconnecting, she tries to kill him as a nuisance but fails. Kou interprets this violence as her unwillingness to lose his friendship. After turning him into her vampire offspring, their relationship shifts to a parent-child dynamic. She cares deeply, expressing distress when Anko Uguisu injures him and promising new memories, though she continues flirting in his presence. She ultimately accepts his departure, acknowledging "young birds must leave the nest" despite potential loneliness. Hostility defines her interactions with Nazuna Nanakusa, marked by mutual disdain and physical confrontations. Seri criticizes Nazuna for associating with humans without turning them, leading to clashes where Nazuna leaves her battered. While superficially supporting Nazuna and Kou, she dismisses their individuality, suggesting stereotypical couple activities despite Nazuna's aversion. Later encounters escalate into fights and insults. Seri questions Nazuna's secrecy about Anko Uguisu's identity after Anko injures Akihito, showing surprise at Nazuna's subsequent accountability. Animosity peaks towards Anko Uguisu after Anko stabs Akihito and shoots Seri in the head. During a tense rooftop meeting before Anko's departure, Seri accepts her apology and quickly forgives her, proposing they share a drink. As a vampire, she possesses immortality, levitation, phasing, superhuman speed, durability, strength, accelerated regeneration, and supernatural charm. Her development reveals a struggle with emotional connection. Initially viewing humans as servants or food, she gradually acknowledges meaningful bonds, shown in her tearful admission about Akihito and reconciliation with former adversaries. She adapts to parent-like responsibilities for her offspring while confronting loneliness upon their independence.