Akuma no Juusanya

Madeline, an 11-year-old girl, lives out of the way in a remote mansion in the woods of southern England with her younger brother Dion, her beautiful mother, and their servant Moira. One day, Madeline meets and befriends some village children. At that time, the gossip was full of rumors of a number of murders in London, said to be the work of a vampire. Whereupon, an eerie shadow creeps into Madeline's peaceful and happy surroundings...

(Source: Kodansha, translated)