Scarlet Slave (Black Butler fanfic)

The first installment in "The Seraphim" series

So much confusion for a girl like young Annabel to withstand. Her father left when she was only a baby. Her brother is seen as dark but a fighter. Her mother is an older, brittle lady who has sent Annabel to the streets in search of food. But one thing leads to another and a strange encounter offers her a life of blood and neck slicing, then pampered luxury and endless drama, all served on a golden platter twined with ivory patterns. How did it all happen? Well..... It all started with a boy named Ciel Phantomhive.

(this story follows the plot line of the anime since I haven't caught up to the manga)