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.

Kou Yamori is an average middle school student who struggles with grasping the complex concept of love. Because he sees little sense in surrendering to the norm, he soon stops going to school. Plagued with insomnia due to his idleness, Kou begins roaming the lonesome streets at night. One night, Kou encounters a bizarre girl named Nazuna Nanakusa who believes that people stay awake during the night because they are dissatisfied with how they spent their day and cannot rest until they release their inhibitions. Nazuna offers to help Kou with his sleep issues and invites him over to her place, where she convinces him to share a futon with her. Feeling uncomfortable, Kou only pretends to doze off—which is when Nazuna suddenly bites his neck and reveals herself to be a vampire! While Kou thinks the bite will turn him into a vampire, the specifics of transforming are not that simple. In order to change, he must be bitten by someone he truly loves. Ready to let go of his dreary mortal life, Kou decides on a new goal: he will fall in love with Nazuna and become a vampire.