Tsukuyomi Moon Phase Vol 1

Tsukuyomi: Moon Phase by Keitaro Arima. A Fantasy manga rated Older Teen, published in English by Tokyopop.

Photographer Kouhei Midou is investigating a haunted castle when he meets Hazuki, a young vampire girl who bites him and makes him her servant. She follows him home, and he finds himself protecting her from the vampires who want her back.