Kamiyadori(2003)

In a dark future, a biological disease that transforms humans into monsters called the Kamiyadori plagues the city. The peacekeeping forces include a specially trained team called the the Right Arms. These agents must keep tight control on those who are infected - and the only salvation they offer is execution! But when one Right Arms officer is unable to kill a young boy and his sister, he sets off a chain of events that may bring a ray of hope to a world filled with despair and chaos...

(Source: VIZ Media)