Manga by author Kagesaki Yuna

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.

Hirose Goushi has a huge sister complex. So huge, he moves from his home town to Tokyo to attend Myouzen University in order to escape it!Three years later, Goushi's little sister Noa shows up and informs him that she's taking the Myouzen University entrance exam and that she will be moving in if she passed. Little does Goushi know, she has a similarly large (if not larger) brother complex.Read as Goushi attempts to hide his feelings for his sister, while she purposefully sets him up for failure.