Anko Uguisu, born Kyouko Mejiro, attended night school where she formed a close friendship with Nazuna Nanakusa. Initially a loner fascinated by detective stories, Kyouko shared intimate personal details with Nazuna, including her father's affair, amidst mutual sexual attraction. This friendship shattered traumatically when her father, transformed into a vampire, murdered her mother. Kyouko killed him in self-defense and sought Nazuna's help to become a vampire. The transformation failed due to Kyouko's lack of genuine romantic love. This failure and her family's destruction fueled intense hatred toward all vampires, driving her to dedicate her life to their eradication under her new identity. Specializing in exploiting vampires' personal mementos to kill them, Anko first encountered Kou Yamori while investigating a vampire's disappearance. Recognizing Kou's desire to become a vampire, she actively opposed his goal, warning him of vampire-caused suffering. She demonstrated her methods by killing a former teacher at Kou's school—a vampire who had starved for ten years after being turned without understanding his condition. Anko allowed him to die in sunlight, framing it as a mercy killing to preserve his humanity. She later attempted to manipulate Kou by offering her body while secretly arranging police intervention to force him home. Anko's vendetta climaxed during a Halloween event where she attacked multiple vampires to lure Nazuna into confrontation. She brutally injured Nazuna, including shooting her in the eye, and threatened Kou's life to provoke Nazuna into killing her. This act was part of a plan to expose vampire existence through her death and trigger an investigation into her past. Kou intervened, revealing her suicidal intent. After her plan failed, Anko attempted suicide but was stopped by Kou. She confessed her decade-long hatred served as a coping mechanism for suicidal ideation, admitting she felt like an "empty shell" without it. Following this, Anko abandoned vampire hunting, expressed regret for her actions, and apologized to those she harmed, including the shot Nico Hirata. She struggled to adjust to normal life, lacking experiences like friendships or romance due to her single-minded pursuit of revenge. Despite this, she retained a connection to the supernatural world, helping Kou confront Kiku Hoshimi—the vampire who turned her father—to achieve closure. Feeling purposeless in her hometown afterward, she moved to Vietnam with the vampire Susuki to study vampires, though she eventually returned to Japan. Anko's appearance featured short brown hair, often tied in a ponytail or bun, and round glasses inherited from her father. She typically wore a beige trench coat, black skirt, turtleneck, heeled boots, and black gloves. As a teenager in a baggy school uniform, her expressions appeared more lively compared to her older self's vacant eyes. For undercover work, she used disguises like a grim reaper or policewoman costume. Her personality blended sharp observation with instability. She presented as straightforward and sociable, often teasing others, but could shift instantly to seriousness or psychosis, laughing maniacally while harming vampires. She disregarded legal boundaries, carrying weapons like a handgun or butterfly knife, and justified actions based on personal beliefs. Her trauma manifested as recklessness, minimal self-preservation, and sadism toward vampires. After renouncing vengeance, she adopted a calmer, analytical demeanor, though she continued to undervalue her life, daring vampires to kill her. She also exhibited a goofy side, including drunken dirty jokes and awkward romantic overtures toward both genders, including middle-school-aged individuals.