Plot
A wormhole suddenly appears inside Class 2's room and absorbs the students there and Class 1 students Naofumi Iwatani, Raphtalia, and Filo who are only visiting. They arrive in another world, except Ainz Ooal Gown and Chomusuke who have arrived first and found themselves inside a facility housing golems that are similar from his world. The students get attacked by a large golem, resulting in them getting split up. The group consisting of Mare Bello Fiore, Aqua, Rem, Ram, Wilibald Koenig, Rhiner Neumann, and Naofumi escapes a swarm of small golems and arrives at a village, where a human named Alec lives. The other group consisting of Shalltear Bloodfallen, Aura Bella Fiora, Demiurge, Darkness, Subaru Natsuki, Puck, Beatrice, Viktoriya Ivanovna "Visha" Serebryakov, and Filo is saved by a girl golem named Pantagruel and brings them to the village, where they reunite with Naofumi's group.
Kazuma Satou, who gets separated from the group alone, follows a girl in a military outfit to the facility and reunites with Ainz. The girl introduces herself as Vera Mitrohina and reveals a sphere device that is capable of traveling between worlds. The three form an alliance to learn about the device. Meanwhile, the other group consisting of Albedo, Cocytus, Megumin, Emilia, Tanya von Degurechaff, Matheus Johann Weiss, Vooren Grantz, and Raphtalia continues to fight a swarm of small golems. At the village, Naofumi and Subaru's groups learn that there is no way home and the golems can be controlled by a ring, but it has been stolen by Vera to bring them back to her world and end the war there. Back at the facility, Vera reveals that they need the "Sign of the Chunibyo" to activate the sphere. After Ainz explained what chūnibyō is and Kazuma pointed out the keyhole looks like an eyepatch, Vera realizes Pantagruel has those features.
Aqua, Subaru, Beatrice, Naofumi, and Pantagruel head out to Tanya's group after their location was found by Visha. Pantagruel confesses about the device at the facility that can bring them home. Upon their return to the village with Tanya's group, Vera takes Pantagruel hostage and reveals to Tanya that she has come from her world and is a spy of the Unified States to the Empire who wants to destroy the latter with golems. Back at the facility, Ainz and Kazuma explore the place when the latter finds a diary of the facility's owner, whom he recognizes as the creator of the Destroyer from his world. Ainz and Kazuma learn that the golem that had destroyed the world where they are now will emerge once the device is activated. Despite the warnings, Vera activates the device, causing the sphere to crack and the golem to emerge.
The students arrive near the facility and fight the golems protecting it. With large golems remaining, the students execute their plan to teleport them inside a large hole and for Megumin to destroy them with her Explosion magic. Kazuma joins his classmates with a golem he found while wandering the forest alone. Inside the facility, Vera learns that Pantagruel can control the golem from the inside, at the cost of her personality ceasing to exist. The students form into small groups to toss Pantagruel toward the golem's left eye. Afterward, the golem, now merged with Pantagruel, destroys its core to reveal the wormhole. Kazuma uses his Steal ability to retrieve Pantagruel from the golem as he enters the wormhole. Pantagruel reunites with Alec and Vera. In a post-credits scene, Subaru finds Garfiel Tinsel and Otto Suwen as transfer students.
