Katta Kirifuda, who loves curry bread more than anything else, hates dueling because he is constantly compared to his older brother, Shobu Kirifuda, a legendary duelist. Despite being the younger brother of a famous champion, Katta initially refuses to duel no matter who invites him. However, his resistance crumbles when he is lured by the promise of curry bread, leading him to participate in a D.M. tournament as a stand-in for his friend Benchan. As Katta duels and begins interacting with his friends and the cards themselves, his feelings about the game gradually start to change. Katta possesses a unique transformation known as Victory Mode, triggered when a V symbol on his forehead glows, which causes a complete shift in his personality into an aggressive, predatory state singularly focused on winning. Early on, he struggles to control this power, but he eventually learns to master it and communicate with the creature spirits he duels with.

The story takes place in a world where the card game Duel Masters connects the real world to a separate Creature World. In this setting, players can bring monsters to life during their duels. Katta's personal history is deeply tied to his brother. When Katta was born, he was in a persistent vegetative state, and his soul wandered outside his body. He was revived when his grandfather stuffed a spicy curry bread into his mouth, which caused him to breathe flames. Before Shobu disappeared, he gave Katta the card Raging Dragon Lord, which Katta keeps encased and wears around his neck. Katta's hatred for dueling stems from his brother's disappearance, but his journey leads him to discover his own dueling identity rather than just being Shobu's brother.

During a dueling tournament, Katta steps in for Dragon Ryu, who reveals himself as a card to protect Princess Puddin. After defeating the villain Onsen and vanquishing the threat of impostors, a new school year begins. Katta is surprised to find Leo Hyakuju, from the idol group YA RA SI, has transferred to his class. Together with this new rival and his eccentric classmates, Katta begins solving all kinds of problems through dueling, leading to an exciting and crazy school life. The plot is driven by conflicts such as Benchan being accused by a mysterious man of stealing a D M card, as well as larger threats involving the Creature World. Katta eventually proves himself as a duelist in his own right, demonstrating the same willingness to fight for others and for the creature world that his brother once showed.