Shinichi is the protagonist of the manga, a thoughtful, compassionate high-school boy whose hand is infected with a Parasite. Shinichi is repeatedly put into difficult positions. He must find a way to peacefully coexist with Migi, the Parasite which has taken over his hand, and reconcile his desire to protect humanity from the Parasites with his desire to keep his own Parasite a secret in order to avoid being killed or used as a laboratory specimen. Like a superhero with a secret identity, he must also find a way to explain away his Parasite-fighting activities, as well as the stress and grief they cause him, to his friends and family. Shinichi's retention of a human mind, emotion, and sensibilities causes other Parasites to see him as a threat. He and his Parasite must defend themselves from attacks by other Parasites, and their ability to think and act independently, and as a team, gives them a tactical edge over normal Parasites.