Earth is quietly invaded by alien parasites which have the ability to crawl through people’s nostrils or ear canal to access their brains, eventually taking full control of their body. Shinichi Izumi manages to partially escape this fate because he happens to be wearing headphones when one of these parasites attempts to control him. The parasite, “Migi”, instead takes up residence in Shinichi’s right hand and the two form a symbiotic relationship with both of their personalities fully intact. Together, they fight against other parasites who devour humans as food.