The Chibi Vampire manga series and its light novel adaptation feature a cast of characters created by Yuna Kagesaki. The series takes place in a fictional Japan where vampires live amongst humans and are slowly dying out from lack of reproduction. Among them is Karin Maaka, an unusual vampire who does not drink blood but instead must inject it into others because her body produces too much. The middle child in a family of vampires, Karin lives like a normal human teenager, attending school and walking in the daylight with no harm to herself. Her parents, Henry and Calera Maaka, along with her older brother Ren and younger sister Anju, worry about her unusual nature. At school Karin meets a new transfer student, the human Kenta Usui, with whom she becomes friends and later falls in love. After he learns her secret, he agrees to help Karin during the day when her vampire family is unable to watch over her. While the awkward couple deal with the issues of a relationship between a human and a vampire, they meet Yuriya Tachibana, a human-vampire hybrid sent by her uncle Glark to look for the "psyche" of vampires. The pair eventually kidnaps Karin, the "Spring of Psyche", and intending that all vampires drink her blood so that it may rejuvenate their species.
The anime television adaptation features character designs by Yumi Nakayama and a slightly modified story. Yuriya, Glark and Bridget do not appear; instead, the Maaka family finds itself targeted by the Sinclair family of vampire hunters. Victor Sinclair wishes to destroy the family, blaming them for his family's "shame" because his ancestor Alfred Sinclair fell in love with Elda Maaka, Karin's grandmother. Victor blames Elda for loving Alfred and filling his life with sadness. Victor's grandson Winner initially aids him in his quest, but develops feelings for Karin who gave him confidence when he questioned his ability to follow his dreams.
Karin Maaka (真紅 果林 Maaka Karin) is descended from a long line of purebred vampires. However, instead of having to drink blood like normal vampires, Karin's body overproduces blood. Generally, once a month she reaches a point where she can no longer hold it in, and she must bite someone to inject them with her blood or else suffer from a massive nosebleed. In the anime, if Karin goes too long without biting someone and tries to hold her blood in, she enters a "berserker"-like state and aggressively attacks the first target she can find. Being near a person suffering misfortune causes Karin's blood to increase ahead of schedule. Due to her unusual situation, Karin lives like a normal human rather than a vampire. She lives in the daylight, is not susceptible to common vampire weaknesses. and lacks the skills normal vampires have. These differences cause her to be somewhat separate from her parents and older brother, whom she only sees for a few hours in the time before she goes to sleep (she spends more time with her younger sister Anju, who has not yet awakened as a vampire). In the first chapter Karin meets Kenta Usui and is dismayed that her blood increases around him. He has a lot of misfortune in his life. Karin resolves to do favors for him and thus reduce his misfortune and her blood problems around him. As the series progresses, Karin falls in love with Kenta. He returns her feelings, though Karin is initially troubled to learn that human-vampire children are born sterile.