Isekai Quartet the Movie: Another World

A wormhole materializes in Class 2's room and pulls in the students. Naofumi Iwatani, Raphtalia, and Filo—who were visiting—vanish into the anomaly, while Ainz Ooal Gown and Chomusuke arrive first in a facility filled with golems. The two groups orient themselves in this alien world as the crossover begins.

Inside the facility, a towering golem launches an assault on the newcomers. The onslaught forces the students to scatter, creating two main factions that must navigate the unfamiliar environment separately. Small golems swarm as the groups search for safety.

Mare Bello Fiore, Aqua, Rem, Ram, Wilibald Koenig, Rhiner Neumann, and Naofumi escape the golem swarm and reach a nearby village. There they meet Alec, a human resident who offers shelter amid the invasion. The group begins to assess their chances of survival in this new world.

The other group—Shalltear Bloodfallen, Aura, Demiurge, Darkness, Subaru, Puck, Beatrice, Viktoriya Serebryakov, and Filo—is rescued by Pantagruel, a girl golem. Pantagruel leads them to the same village where Naofumi's group has arrived, and they are reunited with Naofumi's party. The village becomes a temporary sanctuary from the golem threat.

Kazuma Satou, separated from his group, follows Vera Mitrohina to the facility and reunites with Ainz. Vera reveals a spherical device capable of traveling between worlds. The two allies agree to learn how the device works and what it could mean for their futures.

Albedo, Cocytus, Megumin, Emilia, Tanya von Degurechaff, Matheus Johann Weiss, Vooren Grantz, and Raphtalia continue to battle a swarm of small golems. The ongoing skirmish underscores the persistent threat looming over the village and facility. Their efforts keep the defenders occupied.

In the village, Naofumi and Subaru's groups learn there is no obvious way back home. They discover that golems can be controlled by a ring, but Vera has stolen it to bring everyone to her world and end the war there. The revelation deepens the sense of hopelessness and urgency.

Back at the facility, Vera explains that activation of the sphere requires the 'Sign of the Chunibyo.' Ainz explains the term to Kazuma, noting the keyhole resembles an eyepatch. Vera realizes Pantagruel's appearance matches the Sign, exposing Pantagruel's role in the device.

Aqua, Subaru, Beatrice, Naofumi, and Pantagruel head out to locate Tanya's group after Visha detects their location. They return to the village with Tanya's group, but Vera seizes Pantagruel as a hostage and reveals she is a spy from the Unified States aiming to use golems to reshape the war.

Back at the facility, Ainz and Kazuma explore the place further. Kazuma discovers a diary belonging to the facility's owner, identifying the creator of the Destroyer from his world. They learn that the golem that destroyed their world will emerge when the device is activated.

Vera activates the sphere, causing it to crack and releasing a massive golem. The students rush to defend the facility as waves of golems close in, setting the stage for a desperate defense.

The students coordinate a plan to strike the golems and push Pantagruel toward the golem's left eye. The merged Pantagruel destroys the golem's core, revealing the wormhole. Kazuma uses Steal to recover Pantagruel as she steps into the wormhole, reuniting Pantagruel with Alec and Vera.

In a post-credits scene, Subaru encounters Garfiel Tinsel and Otto Suwen as transfer students. The moment hints at further cross-world connections to come.