Parasyte (2011)

Body horror built on one small, brilliant mistake: the alien parasite meant to take over Shinichi's brain gets stopped and takes his right hand instead. What follows is a long argument between a boy and the cold, curious creature living in his arm, broken up by bodies that open into blades and jaws. Hitoshi Iwaaki's art is plain and almost clinical, which makes every transformation land harder. Choose it for the ethics as much as the gore, because the later chapters ask whether humans deserve the planet and do not flatter us. It won the Kodansha Manga Award in 1993, and Kodansha's English edition finishes the whole story in eight volumes.