In the year 2062, Earth finds itself fiercely battling Artemis—an AI which rebelled against humankind following a grand-scale workforce automation project failure years prior. In the hope of winning the war, a group of three highly skilled human warriors is assembled, known as the guardians of humanity. Empress, the last surviving guardian, wakes up alone in an empty research facility. Unable to recall anything from the past except a place called "Lighthouse No. 8," she begins to search for answers. It is not long before she discovers an impending threat from Artemis—and she is the sole person who can save the world from destruction.

The young but feared sorcerer Zagan is a candidate to become a member of the 13 Archdemons—a group of the strongest sorcerers in the world—following the death of their eldest member, Marchosias. When attending the deceased Archdemon's estate auction, Zagan finds something he did not expect: love at first sight. The sorcerer impulsively spends all his money to take Nephelia, a rare elf slave, back to his castle. Given the girl's mysterious and troubling past, there is a lot for Zagan to uncover about his new companion. However, Zagan's lack of experience with the unfamiliar feeling of love leads to many awkward moments between him and Nephelia, whom he calls by the nickname "Nephy." As the two grow closer and get more comfortable around each other, it becomes increasingly evident that Nephy's feelings might not be so different from Zagan's.

Taiki Inomata, a third-year student in junior high, attends Eimei Academy, an integrated school with a major sports program. Having joined the high school badminton team, Taiki tries to attend open practice as early as possible. But no matter how early he goes, he always arrives second in the gymnasium. The person one step ahead of him is Chinatsu Kano, a first-year student in senior high and Taiki's crush. Chinatsu is the rising star of the basketball team, and the gap between her and Taiki could not be greater. Although Taiki is a decent badminton player, his popularity is nowhere near Chinatsu's, making it even less likely for his feelings to be reciprocated. However, in a strange twist of fate, she ends up living in Taiki's house! Wanting to become a worthy match for Chinatsu, Taiki pursues the same dream as his crush: to partake in the Nationals. Taiki starts training harder than ever before, all for the sake of building a strong relationship with his new housemate.

Second season of Nanatsu no Taizai: Mokushiroku no Yonkishi.