One year after goddess Belldandy emerged from Keiichi Morisato's mirror and promised to stay with him forever, a new threat to their happiness emerges, one that could end the contract between Belldandy and Keiichi.

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]

Otaku siblings Tamotsu and Niwaka Denkigai are shopping in Akihabara when it is overrun by vampiric cosplaying monsters! These creatures, known as "Bugged Ones," can possess anyone they bite and soon they begin causing mayhem across the city. As Tamotsu finds himself at the mercy of one of these creatures, he is rescued by the mysterious baseball bat-wielding Matome Mayonaka. Together, they fight through several more encounters with the Bugged Ones, but before long, Tamotsu is fatally wounded protecting Matome. With no other choice, she revives him as a high level Bugged One—just like her! Tamotsu and Matome, along with excitable otaku cosplayer Arisa Ahokainen, make up the group "The Electric Mayonnaise" and they begin dispatching the Bugged Ones in the only way they know how: by ripping off their clothes and exposing them to sunlight! [Written by MAL Rewrite]