In a world where humans can have their wish granted via the Goddess Help Hotline, a human, Keiichi Morisato, summons the Goddess Belldandy by accident and jokes that she should stay with him forever. Unfortunately for him, his "wish" is granted. Suddenly, Keiichi is now living with this gorgeous woman all alone, causing him to be kicked out of the all-male dormitory he was staying in. But soon, after they find lodging in a Buddhist temple, Keiichi and Belldandy's relationship begins to blossom. Although they are both awkward and rather uncomfortable with one another at first, what awaits these two strangers could turn out to be an unexpected romance. [Written by MAL Rewrite]

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]