Migi is a parasitic alien lifeform that attempts to take over the body of high school student Shinichi Izumi but fails to reach the brain, instead settling in his right hand. This incomplete invasion results in a unique symbiotic bond: Migi retains his own consciousness while Shinichi remains in control of his body. Migi takes his name from the Japanese word for right hand, reflecting his permanent residence. Unlike most parasites that fully consume their host’s brain and feed on human flesh, Migi obtains nourishment from the food Shinichi eats and has no inherent urge to kill humans. His core motivation is survival, both his own and that of his shared body, and he approaches every situation with cold, logical calculation, completely devoid of human emotion. He is initially amoral and pragmatic, willing to harm or threaten Shinichi—even threatening to remove his other limbs—if it ensures their secrecy or safety. However, Migi is also highly intelligent and capable of reasoning; he quickly learns Japanese by reading books in a single night and adapts his strategies based on encounters with other parasites. As the story progresses, Migi develops a growing curiosity about human behavior and emotions, a contrast to Shinichi’s increasing emotional detachment after traumatic events. Their relationship evolves from mutual distrust and necessity into a cooperative partnership, with Migi providing enhanced combat abilities and strategic insights while Shinichi supplies a body and a human perspective. Migi often challenges Shinichi’s moral choices, viewing humans and parasites as equals in a survival-driven world. Notable abilities include shapeshifting his tissue into sharp blades, sensory organs such as eyes and ears, and extendable tendrils; he can harden parts of his body for defense and attack, regenerate from injuries rapidly, and even detach from Shinichi for short periods. He possesses superhuman reflexes, agility, and strength, and can sense other parasites through an unknown signal. Over the course of the story, Migi undergoes significant growth, shifting from a purely instinct-driven entity to one capable of self-sacrifice and contemplation. After absorbing vast amounts of information from the powerful composite parasite Gotou, Migi decides to enter a state of deep dormancy to process everything he has learned, stating he may never fully awaken again. This ending underscores his transformation from a simple survival mechanism into a being that values knowledge and reflection. Migi’s role in the narrative is that of a deuteragonist and foil, serving as both an ally and a mirror that forces Shinichi—and the audience—to question the nature of humanity, morality, and coexistence.