Blood+

Synopsis

Saya Otonashi is a fairly normal high school girl, except that she has no memory of her life before a year ago and needs regular blood transfusions to stay healthy. She encounters a mysterious man playing a cello whose song triggers a vague memory. When Saya goes to the school that night to retrieve her forgotten shoes, the cello player approaches her holding a dagger. Saya flees and runs into a teacher, Mr. Inamine, who is then killed by a monster. Saya runs into the school, locking the door behind her, but the monster easily breaks through. The cello player appears and fights off the monster before grabbing Saya and taking her to safety in a classroom. There he tells her the monster is a chiropteran. Meanwhile, her brother Kai arrives to retrieve her after her friend Kaori brings her shoes to their house, and also encounters the monster. The man kisses Saya, forcing her to drink his blood. He tells her "You must fight now."

(Source: Wikipedia)