Yuma appears as a young boy with tan skin, red eyes, and black and red spiked hair that points out and upward. He wears a red Duel vest with a white hood and a purple tanktop with a green "D" symbol, standing for "Duel". Yuma also wears white pants with designs of three orange moon crescents attached to one another with yellow outlines at the bottom, a white brown-stripe belt, and black with blue streaks shoes with white straps.
At school, he wears a white shirt with red-lined sleeves and collar, a red tie, blue pants and brown shoes. In his nightwear attire, he wears a red-white t-shirt grey pants, and sometimes green slippers, but Yuma mostly goes barefoot around his house.
Yuma had same dream again about the mysterious door demanding him that if he opens this door he will receive a new power but in compensation they will lose their most important thing. Yuma thought about his most important thing as the key reacting making the ground below him suddenly crumbles away causing him to fall into a big hole. Later Yuma witnessed as his friend, Bronk Stone dueling Shark and lose the duel getting his deck taken. Yuma tried to stop them, but end up with Shark breaks his key from his neck and throwing away the pieces. Then he makes the proposal to Yuma to win back Bronk's deck, if he defeated him in a duel. The day before the duel, Bronk gave Yuma the lost piece of Emperor's Key and built so well his confidence again. On the day of the duel,Shark quickly took the lead and pulled Yuma already in the second round for half his life. Yuma's amateur skills seemed to have no chance against Shark. Shark taunted him to give up, Yuma urged that he will not give up because he has always believed in himself.
Yuma's key began to glow brightly again and was brought to the door. Yuma's key is self-repairing and Yuma now had enough courage to open the door with the key. A bright light came out and for a few seconds Yuma seemed to be surrounded by Sphere Field of blank cards that are scattered in all directions. Back in reality, a foreign power was at moment begin to take possession of Shark and he Xyz Summons Number 17: Leviathan Dragon. It looked even worse for Yuma, a strange entity, Astral, appeared next Yuma. Astral told Yuma that he is a duelist. Yuma and Astral initially not familiar, which led to frequent litigation. With help ofAstral, Yuma obtained Number 39: Utopia and win the duel. After the Duel, Shark was back to normal and returned Bronk's Deck as promised.
Since the duel is Astral bound to Yuma, Astral can only be seen and heard by Yuma, why Yuma's friends doubt sometimes about Astral's existence. One day at school, the network mysteriously went down, and Yuma's teacher, Mr. Kay, allowed them to use the day to Duel instead, as they could not access their virtual textbooks with the network down. Yuma Dueled his class's chairman, Caswell, but Astral was not present, so Yuma did not have access to his Extra Deck of "Numbers". As a result, he lost in one-turn defeat without inflicting a single point of damage to Caswell.