The protagonist of the show. Karin is a "blood-producing" vampire. Rather than needing to acquire blood from humans, her body produces too much blood instead (polycythemia). To make matters worse, her blood levels increase dramatically whenever she senses unhappiness in those around her, or if she gets embarrassed about something. This results in frequent nosebleeds, followed by anemic symptoms such as light-headedness, which causes frequent visits to the school nurses office so she can rest. She does not suck blood from her "victims"; rather, she injects her surplus into them instead. This has the effect of making her victims very lively and positive.
Manga:
At one point Karin is rendered unconscious for several days after trying to hold in her blood and suffering a massive nosebleed, during which time her family grows increasingly concerned that her condition would kill her. Her mother journeys to her birthplace in search of answers and learns that Karin is a rare vampire, called the "Spring of Psyche", that is born when the vampire species is struggling. The blood Karin produces can bestow fertility in other vampires. Karin is later kidnapped by vampires who want to feed from her to rejuvenate their own lives, though it will kill Karin in the process. They also plan to impregnate Karin against her will to continue the Psyche's existence. After Kenta and the Marker family save Karin from the Brownlicks, her nose-bleeding ceases, leaving her as though she were a normal human, who will likely grow old and die. Her family erases all of her memories of vampires, including themselves, promising Kenta that they will continue watching over her happiness although she will not know them. At the end of the series, Karin and Kenta have married and are shown to have a teenage daughter named Kanon.
Anime:
In the anime adaptation, the blood-making issue and Karin's capture are not mentioned. Instead, Karin has the opportunity to become a full vampire, which she initially declines, but then pursues after Kenta encourages her. The transformation is interrupted and Karin goes berserk. Kenta comes to her rescue by volunteering to be bitten, ending the berserker rage, confirming their romantic relationship. at the end of the anime she is still "un-vampire", is still dealing with her blood-making issue, still has of all her memories and still lives with her family and spend lots of time with Kenta.
