The action takes place on Sai-Kyō-Jima, also known as The Ultimate Island, a mysterious and isolated piece of land filled with countless unexplored battlefields. From dense wilderness and rocky cliffs to sprawling forests, frozen ice fields, and dark caverns, the island serves as a grand arena where creatures from different eras and species fight to prove their superiority. This film, a special edition of the Sai-Kyo-Oh! Zukan: The Ultimate Tournament television anime, presents two never-before-seen championship matches that will determine the strongest of all.

The first major clash is the Strongest Underwater Special Exhibition Final Match, a prehistoric showdown between the massive marine predator Livyatan melvillei and the formidable Spinosaurus. The second is the Strongest King Dragon League Final Match, which moves from the ancient seas to the realm of myth, pitting the Hindu danava serpent Vritra against the four-legged, winged beast Ōryū from Chinese mythology. These high-stakes battles take place under the observation of the series' guides, including the knowledgeable Mr. Most, who also hosts a quiz activity for the audience, and his companion TT. Adding to the event, VTuber Hayato Kagami from the unit ROF-MAO makes a special appearance and performs the film's opening and ending theme songs. The film runs approximately 50 minutes in length.