Mysterious immortal humans known as "Ajin" first appeared 17 years ago in Africa. Upon their discovery, they were labeled as a threat to mankind, as they might use their powers for evil and were incapable of being destroyed. Since then, whenever an Ajin is found within society, they are to be arrested and taken into custody immediately. Studying hard to become a doctor, Kei Nagai is a high schooler who knows very little about Ajin, only having seen them appear in the news every now and then. Students are taught that these creatures are not considered to be human, but Kei doesn't pay much attention in class. As a result, his perilously little grasp on this subject proves to be completely irrelevant when he survives an accident that was supposed to claim his life, signaling his rebirth as an Ajin and the start of his days of torment. However, as he finds himself alone on the run from the entire world, Kei soon realizes that more of his species may be a lot closer than he thinks. [Written by MAL Rewrite]

After escaping certain death, Kei Nagai and his new companion Kou Nakano plot revenge on Satou, their fellow Ajin who is hellbent on world domination. As Satou embarks on a string of public executions, the human race rushes to come up with a solution to stop the immortal villain. Kei discovers unlikely allies in the form of two former adversaries: high-ranking government official Yuu Tosaki, whose extensive research on Ajin gives him a tactical advantage in the fight against Satou, and Tosaki's Ajin assistant Izumi Shimomura. As his faction continues to gather allies, Kei races against time to put a stop to Satou's crusade before it brings about an end to civilization as he knows it. [Written by MAL Rewrite]

Akira Tachibana, a reserved high school student and former track runner, has not been able to race the same as she used to since she experienced a severe foot injury. And although she is regarded as attractive by her classmates, she is not interested in the boys around school. While working part-time at the Garden Cafe, Akira begins to develop feelings for the manager—a 45-year-old man named Masami Kondou—despite the large age gap. Kondou shows genuine concern and kindness toward the customers of his restaurant, which, while viewed by others as soft or weak, draws Akira to him. Spending time together at the restaurant, they grow closer, which only strengthens her feelings. Weighed down by these uncertain emotions, Akira finally resolves to confess, but what will be the result? [Written by MAL Rewrite]

In a world where dead people turn into books and are stored in the Bantorra Library where anyone who reads a book can learn their past, Bantorra Library is maintained by Armed Librarians who wield psychic powers and their enemy is a religious society known as Sindeki Kyoudan.