Karin's a cute, cheerful high school girl. She loves the sunshine, cooking with garlic, and has a part-time job as a waitress. All in all, she's pretty average... except for one thing. Karin is a vampire, and lives with her parents and two siblings, who are also vampires. But even among them, she's different, for she doesn't take blood but give blood that is increased in her body. Once every month, Karin's blood builds up, and if she doesn't expel it quickly, massive amount of blood will come out her nose (a major nosebleed). And one day at school she meets Kenta Usui and gets the feeling of a nosebleed at first site. It seems Karin never has a "right way" for her problems.