Gehigarriak

Nyanpire is a doujinshi manga series created by Yukiusa that was then turned into a twelve part animated series by Gonzo.

Plot (from wiki): A small abandoned kitten is rescued by a vampire, who feeds him some of his blood, allowing him to be reborn as a vampire cat named Nyanpire. The series follows Nyanpire as he spends his days living with his human owner, Misaki, and meeting other cats.