にゃんぱいあ -The Gothic World of Nyanpire-
A 2009 doujin by Yukiusa, adapted into a 2011 anime by GONZO.
The story follows a black cat who was abandoned and left to starve. Just before the cat's life was to be extinguished, a vampire emerged from the darkness and gave it blood. Now, "Nyanpire", it lives as a seemingly ordinary house cat raised by a human girl.