For our first recommendation, we have Vampire Knight, vol. 1 by Matsuri Hino.
Cross Academy is a high school with a secret. There is a day class for ordinary humans, and a night class for a beautiful elite-- who happen to be vampires.
Yuki Cross and her adoptive brother Zero Kiryu are Guardians, members of the day class whose job it is to protect the secret of the night class, and protect the lives of the day class.
When she was 5 years old, Yuki was attacked by a vampire, but was saved by the beautiful, pacifist vampire Kaname. He took her to Cross Academy, where she was taken in by the headmaster, who believes in peace between humans and vampires.
Now, at 15, she helps the headmaster in his cause to educate vampires and promote understanding between the two groups in thanks for Kaname's rescue-- and because she's falling in love with him.
Meanwhile, Zero would desire nothing more than to kill all vampires, in revenge of the vampires who murdered his entire family four years ago. But more happened that night than he has ever let on.
Can Yuki balance her loyalties to the two men who mean the most to her?
Vampire Knight is rated T+ for incidences of violence and mild language