Kei Nagai (Takeru Satoh) dies in a car accident, but his body is recovered and he is revived. From the accident, Kei learns that he is a type of immortal known as Ajin (demi-human). Ajin are considered dangerous by humans. Kei as an Ajin is found by the government and sent to a research facility. There, he is held in custody and undergoes painful experiments.Sato is also an Ajin and a terrorist. He is the only one to extend a helping hand to Kei, but Kei can't take part in Sato's plans to commit mass murders against humans.