Mammoth

Mammoth (マンモス) is a manga written by Buronson and illustrated by Konari Takaki.

Plot
When gentle giant police officer Ippei Hyodo is forced to witness the brutal murder of both his younger sister and police partner, the gentle "Elephant" becomes a "Mammoth" overnight and goes above the law to slowly pick off each man standing between him and his loved one's assassin.