As the Daihasei Festival begins, Uiharu and Saten enjoy themselves, while Kuroko sees to her Judgment duties. Mikoto and Kongo run an eventful three-legged race against teams from other schools. A plot involving MEMBER begins going into motion.

Ringo focuses on developing the item Tsukasa requested while he endures the weight of that request. Shinobu continues to gather information, but shows concern for Jeanne when she uncovers the Azure Brigade's suspicious activity. Meanwhile, a plague strikes the city. Its treatment is beyond the doctors of this other world, and with the group's reserves of medical supplies running low, the patients are facing the risk of death. When the local Medical Guild comes to insult the Seven-Light Faith for failing to save their patients, Akatsuki gets mad. That's when the world's greatest doctor, Kanzaki Keine responds to his spirit and declares that she will make medicine to save them all.

With the paper-making process about to begin, Main can't hide her excitement as she and Lutz go to meet Benno as per his invitation. He reveals that he is willing to arrange for all the equipment and materials they need to make the paper, but the ensuing conversation makes Lutz see Main in a very different light.

Grand Dragon Leviathan’s thunderous roars unleash hundred-foot tall waves worldwide to destroy every town and city on Earth and wash away all traces of humanity! How can Yugi’s simple soul stop the annihilation of the planet from the greatest natural disaster in history? Billions of lives are at stake in the thrilling conclusion where failure means extinction!

It’s the brawl for it all! All the monsters of Earth join forces with the survivors of the monster domain for an epic showdown against Grand Dragon Leviathan with the fate of both worlds hanging in the balance! But the tide of battle is turning against our heroes as Grand Dragon Leviathan unfurls gruesome tentacles to snatch Yugi and his crew and absorb them into its body!

Dartz calls forth Divine Serpent Geh, a sinister snake with infinite attack points! Yugi counters by joining the three legendary dragon knights into the mighty Timaeus the Knight of Destiny, but is that enough to combat a monster with limitless strength? As the great forces clash, the gateway opens for the final endgame as the world-devourer Grand Dragon Leviathan and the legendary Atlantis rise out of its watery grave!