Vampire Dormitory 3

Mito, who has no family to rely on, lives on the streets, disguised as a boy. Ruka, an otaku vampire who's only interested in 2-D girls, saves her from a perilous situation and makes her an offer: become his subservient thrall from which he can feed whenever he wants, and she can live with him-in the boys' dorm. Because her very existence depends on her secret not being found out, every day is a new danger-to say nothing of that vampire!