They come from silence and darkness. They descend from the sky. They are hungry for human flesh. They are everywhere. They are Parasites, alien creatures that attack and take control of humans to survive. Once they infect their victims, they can transform into deadly forms: giant-toothed monsters, winged demons, creatures with knife-like hands... Seventeen-year-old Izumi Shinichi lives with his parents in a quiet neighborhood in Tokyo. One night, worm-like aliens known as Parasites invade the world, entering humans through their ears or noses to take control of their brains. While Shinichi is asleep, a Parasite tries to enter through his ear. However, because Shinichi is wearing headphones, the Parasite fails and enters his right arm, taking control of it. This Parasite is named Migi. Shinichi prevents Migi from reaching his brain. Thus, both manage to retain their personalities and mental health. As the duo encounters other Parasites, they begin to form a strong bond to survive, using their unusual situation to their advantage. The pair decides to fight against other Parasites, determined to protect Shinichi's human brain from being corrupted. With Migi's help, Shinichi feels compelled to fight against the Parasites that mercilessly devour humans.
