"Ajin" is a dark fantasy anime series based on the manga by Gamon Sakurai. The story centers on Kei Nagai, a high school student who discovers he is an Ajin, a rare type of immortal human with regenerative abilities. Ajin are feared and hunted by society due to their perceived threat and the mysterious phenomena surrounding them, such as the ability to summon invisible, ghost-like entities called IBM (Invisible Black Matter). After a fatal accident reveals his immortality, Kei becomes a fugitive, pursued by government forces and bounty hunters eager to exploit Ajin for scientific experiments.

As Kei evades capture, he encounters other Ajin, including Sato, a charismatic and ruthless Ajin who leads a militant group aiming to overthrow the government and establish a world where Ajin are no longer persecuted. Sato’s methods are extreme, involving acts of terrorism and violence, which force Kei to confront his own morality and the ethical dilemmas of immortality. Kei’s journey is marked by alliances with both humans and Ajin, including his friend Kaito, who remains loyal despite the dangers, and Izumi Shimomura, a government agent and fellow Ajin who struggles with her dual identity.

The narrative explores themes of survival, discrimination, and the consequences of immortality, as Kei navigates a world that views him as a monster. The series delves into the psychological and physical toll of being an Ajin, as well as the societal fear and prejudice that drive the conflict between humans and Ajin. The plot is driven by intense action sequences, strategic battles, and moral quandaries, with Kei’s character evolving from a reluctant survivor to a more proactive figure in the fight for Ajin rights. The story’s tension is heightened by the unpredictable nature of the IBM and the ever-present threat of capture or death, even for immortals.