Arachnid

Arachnid is an ongoing shounen manga written by Murata Shinya and illustrated by Ifuji Shinsen.

Plot
Alice is a senior high school student who lives with an uncle that spends his time tormenting her everyday. One day, Alice witnesses the death of her uncle by the hands of an assassin called "Kumo" (Arachnid in Japanese). She then falls unconscious, and upon waking up, she finds out that she's in Kumo's house. Now, this Alice who no longer has any family is being raised by the assassin himself.

Official
http://www.jp.square-enix.com/magazine/joker/series/arachnid/index.html