The story revolves around the title character, Karin, the middle child in a family of vampires who immigrated to Japan two centuries earlier. However, Karin is different from the rest of the family in that she produces blood instead of feeding on it. Because of her unusual condition, Karin lives her life just as an ordinary teenage girl would, despite being considered something of a freak by her family. She is able to venture outside during the day and attend high school, and follows the sleep pattern of normal humans. However, the general peacefulness of her life is disrupted with the arrival of a new transfer student, Kenta Usui…