A new student, Ryuji Otogi, defeats Jonouchi in a game of Duel Monsters, forcing Jonouchi to become his servant. Ryuji forces Jonouchi to wear a dog costume and humiliates him in public, forcing Yugi to challenge Duke to a duel. However, this will not be a Duel Monsters duel, but a new game named Dungeon Dice Monsters!