A wormhole suddenly opens inside Class 2's room and swallows the students there, along with the visiting trio Naofumi Iwatani, Raphtalia, and Filo. The trio arrive in a strange new world just as Ainz Ooal Gown Satoshi Hino and his companion Chomusuke Hitomi Nabatame had already breached a facility housing golems that feel oddly familiar from his own realm. The initial arrival shakes the group, and a massive golem attacks, forcing the students to split into separate paths.
One team, led by Mare Bello Fiore Yumi Uchiyama alongside Aqua Sora Amamiya, Rem Inori Minase, Ram Rie Murakawa, Willibald Koenig Jun Kasama, Rhiner Neumann Masayuki Katou, and Naofumi Iwatani, battles its way to a village where a human named Alec lives, escaping a swarm of smaller golems along the route. Their journey is marked by a cautious hope for safety and a growing sense that they’re far from home. The other team, comprising Shalltear Bloodfallen Sumire Uesaka, Aura Bella Fiora Emiri Kato, Demiurge Masayuki Katou, Darkness Ai Kayano, Subaru Natsuki Yusuke Kobayashi, Puck Minami Tanaka, Beatrice Satomi Arai, Viktoriya Ivanovna 'Visha' Serebryakov Saori Hayami, and Filo Rina Hidaka are saved by Pantagruel, a girl golem, and brought to the same village, reuniting them with Naofumi's group.
Meanwhile, Kazuma Satou Jun Fukushima ends up separated from the others and follows a uniformed girl to the same facility, where he reconnects with Ainz Ooal Gown. The girl introduces Vera Mitrohina Nana Mizuki and reveals a sphere device capable of traveling between worlds. The three decide to team up to learn more about the device. Back with the village groups, the search for a way home continues, and they learn that the golems can be controlled by a ring, though Vera has stolen it to pull everyone back to her world and end the war there. Vera then explains that activating the sphere requires the “Sign of the Chunibyo,” a clue that leads them to Pantagruel, whose features resemble the eyepatch keyhole the group has been tracking.
Aqua Sora Amamiya, Subaru Natsuki Yusuke Kobayashi, Beatrice Satomi Arai, Naofumi Iwatani, and Pantagruel head toward Tanya von Degurechaff's group after Visha Saori Hayami locates them. Pantagruel finally confesses that the device at the facility could send them home. When they return to the village, Vera abducts Pantagruel and reveals to Tanya that she is from Vera's world and serves as a spy for the Unified States, tasked with destroying the Empire through golems. This revelation adds a sharp edge to the mission: everyone must decide whom to trust and how to use the device to their advantage.
Back at the facility, Ainz and Kazuma delve deeper and discover a diary belonging to the facility's owner, whom Kazuma recognizes as the creator of the Destroyer from his own world. The diary hints at a looming threat—the very golem that destroyed their world could emerge once the device is activated. Despite warnings, Vera activates the device, fracturing the sphere and triggering the arrival of the menacing golem.
As events unfold, the students converge near the facility to confront the golems guarding it. They orchestrate a bold plan to teleport the swarming giants into a deep hole, while Megumin Rie Takahashi unleashes explosive magic to thin their ranks. Kazuma Jun Fukushima joins the fray with a golem he finds wandering the forest, lending his skills to the desperate mission. Inside the facility, Vera learns that Pantagruel can control the golem from within, but at the cost of Pantagruel’s own personality fading away. The students split into teams to aim Pantagruel toward the golem’s left eye, triggering a climactic merge that allows Pantagruel to destroy the golem’s core and reveal a wormhole.
In a final twist, Kazuma uses his Steal ability to retrieve Pantagruel from the golem as he steps into the wormhole, reuniting Pantagruel with Alec and Vera. The post-credits scene hints at new possibilities as Subaru encounters Garfiel Tinsel and Otto Suwen as transfer students, leaving the fate of their worlds uncertain but full of potential collaborative sparks, new loyalties, and the enduring question of how many doors a single jump between worlds might open.
