Vampire Dormitory.

After Mito loses her parents and is fired from her job, she must fend for herself on the streets disguised as a boy. She comes across a stranger named Ruka and learns his dark secret—he's a vampire! Ruka invites Mito, still in disguise, to live in an all-boys dorm. Mito exchanges her blood for a place to stay, but a budding romance and her true identity threaten all that hangs in the balance.