"Ajin: Demi-Human" is a manga series that explores the existence of immortal beings known as Ajin, who are discovered to possess regenerative abilities and the capacity to summon an invisible, supernatural force called a "Black Ghost." The story begins with Kei Nagai, a high school student who, after a fatal accident, discovers he is an Ajin. This revelation thrusts him into a world of persecution and experimentation, as Ajin are considered dangerous and are hunted by governments and organizations for research purposes. Kei's life spirals into chaos as he becomes a fugitive, pursued relentlessly by authorities and bounty hunters. Along the way, he encounters other Ajin, including Sato, a charismatic and ruthless Ajin who leads a militant group aiming to overthrow the oppressive systems targeting their kind. Sato's methods are extreme, often involving violent confrontations with government forces, and his actions force Kei to confront the moral complexities of his own immortality. The narrative delves into the ethical dilemmas surrounding the treatment of Ajin, who are often subjected to inhumane experiments due to their inability to die. Kei struggles with his identity as an Ajin, grappling with the fear of being hunted and the temptation to use his powers for self-preservation. His journey is marked by alliances with other Ajin, such as Izumi Shimomura, a former government agent turned Ajin, and Tanaka, a fellow fugitive with a tragic past. The series is notable for its intense action sequences, particularly the battles involving the Black Ghosts, which are manifestations of the Ajin's will and serve as powerful weapons. The dynamics between the Ajin and their Black Ghosts add a layer of psychological depth, as the entities often reflect the inner turmoil and desires of their summoners. As the story progresses, Kei is forced to navigate a world where trust is scarce, and survival often comes at a moral cost. The conflict between Sato's radical faction and the government escalates, leading to large-scale confrontations that test the limits of the Ajin's abilities and resolve. The series explores themes of identity, humanity, and the consequences of immortality, set against a backdrop of relentless action and political intrigue.