Alto Goldfilled, a diligent student at the Ortigia Academy of Magic, aspires to become a powerful sorcerer. But he is unable to become one as, despite his excellent grades and strong commitment to his studies, he fails his summoning class. With the threat of repeating a year hanging over his head, Alto tries following an old, worn-out grimoire in a desperate attempt to resolve his situation. To his surprise, he succeeds and summons a powerful demon named Vermeil. As a sign of gratitude for releasing her, Vermeil agrees to become Alto's familiar, sealing their relationship with a deep kiss. Little does Alto know what else he is capable of and what Vermeil's past hides.

After finishing their "debut," Kate, Emilico and three other pairs who started with them begin a new life as adults.

Life back on the cruise following the Island Special Examination is anything but smooth sailing. Almost immediately after their return, the first-year students of Tokyo Metropolitan Advanced Nurturing High School face yet another special exam, with both class and individual points on the line. In addition to the complicated ruleset, more issues arise in the form of Kakeru Ryuuen and Kei Karuizawa. Angered by the previous test's outcome, Ryuuen is dead set on outdoing every class in the new challenge using any means necessary. Meanwhile, Karuizawa, a crucial pillar of Class D, is close to crumbling under the pressure of her past. The stage is now set for Kiyotaka Ayanokouji to once again—using the full extent of his planning, foresight, and ruthless manipulation—steer Class D to victory as dangerously close enemy forces try to bring it down.

E-Rantel, the capital city of the newly established Sorcerer Kingdom, suffers from a dire shortage of goods. Once a prosperous city known for its trade, it now faces a crisis due to its caution—or even fear—of its king, Ainz Ooal Gown. To make amends, Ainz sends Albedo to the city as a diplomatic envoy. Meanwhile, the cardinals of the Slane Theocracy discuss how to retaliate against Ainz after his attack crippled the Re-Estize Kingdom's army, plotting for the Baharuth Empire to take over the Sorcerer Kingdom. However, when Emperor Jircniv Rune Farlord El Nix arranges a meeting with the Theocracy's messengers at a colosseum, he is confronted by none other than Ainz himself. With their secret gathering now out in the open, the emperor and his guests learn that Ainz has challenged the Warrior King, the empire's greatest fighter, to a duel. With Ainz's motivations beyond his comprehension, Jircniv can do nothing but watch as humanity's future changes before his very eyes.