Kei Nagai’s transition from a focused medical student to a legendary fugitive begins the moment he stands up after a fatal truck accident, revealing to the world that he is an immortal entity also known as an *Ajin: Demi-Human*. This shocking resurrection instantly brands him a target for government agencies that view his kind as biological property to be captured and subjected to horrific, endless experimentation. Forced to flee the only life he has ever known, Kei must rely on his cold, analytical mind and the manifestation of a mysterious "Black Ghost" that often acts beyond his control. His journey is defined by a deep internal conflict as he struggles to maintain his humanity and moral compass while his own growing emotional detachment threatens to consume him.

The stakes explode when the ruthless and charismatic veteran Satou launches a campaign of high-stakes terrorism, forcing Kei into a brutal tactical war between two species. As he navigates this deadly game of supernatural combat and political intrigue, the conflict shifts from a simple hunt for survival into a national crisis that challenges his very identity. Despite the relentless pursuit of the Anti-Ajin Special Force and the blood-soaked vision of his rivals, Kei remains driven by a singular, unwavering goal: to reclaim his freedom and secure the quiet, ordinary life that was stolen from him. No matter how many times he must die to reach it, his resolve to protect his world and live on his own terms never wavers.