Gemeinsam wollen Yuma und seine Freunde mit Dextra und Nistro das Geheimnis des versunkenen Kolosseums entschlüsseln. Dort warten auch schon eine weitere mythyrianische Karte und ein Duell auf sie …
Yuma and the others travel to Spartan City in Rome, where they learn of a duel tournament that Nistro is participating in, with Dextra serving as his manager. Nistro explains to Yuma how he and Dextra, who both grew up on the streets, found hope in Duel Monsters and wanted to give that same hope to children using his new "Star Man" persona. They then tell them about a legend involve a fighter who made friends with a rival, but was ultimately betrayed and executed, stating that the colosseum where the sealed Number lies is somewhere at the bottom of a lake. Later that night, Alito sets off some bombs to drain the lake, revealing the hidden colosseum. Alito enters the colosseum and defeats the sealed Number's guardian, claiming the Number just as Yuma and the others arrive at the colosseum. Alito, who seems to have no recollection of his friendship with Yuma, puts Nistro under his control and challenges Yuma and Dextra to a tag duel. Yuma summons out Utopia whilst Nistro summons Alito's new Number, Number 54: Lion Heart, dealing a large amount of damage to both Yuma and himself.
