Yuma Tsukumo was a young Duelist with big dreams of becoming the greatest. Despite his amateur skills, he found himself reluctantly partnered with a Dueling spirit called Astral. Together, they pursued the "Numbers" to recover Astral's scattered memories, becoming Number Hunters along the way and cultivating Yuma's Dueling abilities. After emerging victorious in the World Duel Carnival, Yuma became the Duel Champion of Heartland City.
Yuma was not alone in his journey, as he met two boys named Dumon and Reginald Kastle at school. Dumon, an Emperor of the Barian World, was initially cold and distant, but as Yuma got to know him better, he realized that Dumon cared deeply for his fellow Barians and prioritized the safety of his world above all else. Reginald Kastle, on the other hand, started off as an arrogant and callous person but grew humble over time. Little did Yuma know that Reginald Kastle was actually Nash, the leader of the Seven Barian Emperors.
As Yuma's bond with Dumon and Reginald/Nash deepened, he found himself falling in love with them. Despite their differences and the challenges they faced, their friendship blossomed into something more meaningful. Yuma's hasty, energetic nature complemented Dumon's level-headedness, while Reginald/Nash's loyalty and determination inspired him to push forward.
But Yuma's heart belonged to someone else, someone who had been by his side through thick and thin - Shark. Shark, with his dark blue eyes and tentacle-like hair, was a loner with a soft side that he only showed to his sister Rio Kastle and Yuma. Their friendship went beyond Dueling, as Shark trusted Yuma with his deepest secrets and even entrusted him with a card that would help them win a crucial Duel.
Despite the challenges they faced and the battles they fought, Yuma, Dumon, Reginald/Nash, and Shark remained steadfast in their bond. Their love for each other grew stronger with each passing day, as they supported each other through the toughest of times.
Yuma's world was turned upside down when he discovered that he was the Original Number's other half that had been separated from him during Astral's battle with Don Thousand long ago. As he delved deeper into his destiny and the truths that connected him to his parents, Yuma realized that he was the key to bringing an end to the Interdimensional War between Astral World and Barian World.
With the support of his friends and the love that bound them together, Yuma faced the greatest challenge of his life. And as he dueled his way to victory, he knew that no matter what obstacles stood in his way, he would always have Dumon, Reginald/Nash, and Shark by his side, ready to fight alongside him until the end.
