Yuma aims to be the Duel Champion, and forms a Dueling Team with Kotori, Tetsuo and Takashi, named Team ZEXAL. Astral is a Dueling Ghost who helps Yuma in his Duels, but he can only be seen by him. By that way, when Yuma talks to him, the others think he is talking to himself. In addition with Yuma's arriving late for his team's first meeting, Kotori and Takashi get worried about Yuma being the leader, and Tetsuo challenges him to a Duel - if Tetsuo wins, he will be the leader. Yuma accepts the challenge, and wins, so that others accept him as the leader.
Some time later, after defeating some kids, Yuma gets cheered up, but Astral tells him he is only able to win due to his help, and that he relies on monsters too much. Yuma says that intensely attacking with monsters is more interesting and that he can win without Astral's help. Tokunosuke hears what Yuma says about his strategy and goes to Team ZEXAL to tell them that he doesn't have any friends, so he doesn't really have anyone he could Duel with. Hearing that, Yuma Duels Tokunosuke. During the Duel, Yuma plays very recklessly, falling in Tokunosuke's tricks, although Astral kept warning him about them. However, Astral then backs helping Yuma, and he manages to win.
After Tokunosuke loses to Yuma, he explains that he wanted to enter a certain Dueling Team, Team Shark, and that he would only be accepted if he defeated the leader of the ZEXAL Team, Yuma. Then, the leader of the Team, a boy nicknamed Shark, shows up. Tokunosuke rushes up, but he is despised by Shark's Team. Yuma gets angry with that, and confronts Shark.
Shark calls Team ZEXAL weak, and challenges Yuma to a Duel under some conditions: first, they will bet their teams' badges, which symbolizes the pride of the team; and second, if Yuma lose, Tokunosuke will enter Shark's team as a slave who does every work. With no other option, Yuma accepts the Duel.
Astral instructs Yuma on how to Duel, but Yuma doesn't listen to him and does things his way, causing a mix-up which led him to lose. However, when Shark attempts to take his badge, he sees Yuma's cards, and notes that Yuma could have won. Because of that, he declares the dispute as invalid, and tells Yuma that the next time they Duel, he'll use his true strength.
After the loss, Yuma's friends are worried about him, and go visit him. However, they are surprised seeing Yuma isn't feeling down at all - actually, that made him want to become stronger. Takashi suggests modifying Yuma's Deck in order to improve it, and everyone decides to help out.
Yuma uses a Deck similar to his anime Deck, with some additions from the OCG.
Before Yuma and his team face Master Evil, they discuss about the possibility of Master Evil having watched their Duels and developed a strategy to counter their moves, so they help Yuma slightly rebuild his Deck.