Parasyte: After My Left Hand Was Infected, I Went on a Killing Spree

(Dark themes, villain protagonist, a little bit deranged. Do not read if you like saintly protagonists.)

(The protagonist of Parasyte, Shinichi Izumi, is far too saintly. I want to show what happens when a deranged serial killer gets infected by a parasite.)

One day, green spores suddenly began to drift down from the sky, like a snowfall of green. One landed near Chu Ren, a death-row inmate. A tiny worm crawled out of the spore, ready to burrow into Chu Ren's brain. Then it failed, and had no choice but to parasitize his left hand instead.

Afterward, Chu Ren's left hand became an intelligent creature known as a Parasyte, and helped him break out of prison. Meanwhile, gruesome murder and dismemberment cases began occurring all over the world.

Chu Ren: “Xiao Zuo, from now on, stick with me and help me wipe out the human race.”

(I'm no good at writing introductions, so please read the story.)