Parasyte -the maxim-

They arrived in silence and darkness, descending from the skies with a hunger for human flesh. Parasites - alien creatures who must invade and take control of a human host to survive - have come to Earth. No one knows their secret except high school student, Shinichi Izumi, who's right hand has been invaded by an alien parasite. Shinichi and Migi, the parasite in his hand, begrudgingly form a friendship and find themselves caught in the middle of a war between humans and parasites. (Source: Crunchy Roll)