Kiseijuu: Sei no Kakuritsu

All of a sudden, they arrived: parasitic aliens that descended upon Earth and quickly infiltrated humanity by burrowing into the brains of vulnerable targets. These insatiable beings acquire full control of their host and are able to morph into a variety of forms in order to feed on unsuspecting prey. Sixteen-year-old high school student Shinichi Izumi falls victim to one of these parasites, but it fails to take over his brain, ending up in his right hand instead. Unable to relocate, the parasite, now named Migi, has no choice but to rely on Shinichi in order to stay alive. Thus, the pair is forced into an uneasy coexistence and must defend themselves from hostile parasites that hope to eradicate this new threat to their species. The 17-year-old Izumi Shinichi lives with his mother and father in a quiet neighborhood in Tokyo. One night, worm-like aliens called Parasytes invade Earth, taking over the brains of human hosts by entering through their ears or noses. One Parasytes attempts to crawl into Shinichi's ear while he sleeps, but fails since he is wearing headphones, and enters his body by burrowing into his arm instead, taking over his right hand and is named Migi.