Yu-Gi-Oh! ZEXAL - Episode 001
Barian World (former), Earth and all human friends
Reginald Kastle, better known by his nickname Shark, is a pro duelist who made it to the National Duel Circuit, but he was unexpectedly disqualified. Shark is the school's #1 bully who's always sharpening his teeth and setting his eyes on taking down his next prey! Shark is close friends with Yuma Tsukumo and fights the Barian threat alongside him and Kite Tenjo. He is later revealed to be the leader of Seven Barian Emperors, Nash.
In his past life, Reginald was a king alongside his sister, Rio Kastle being a princess. They lived in United Lands of the Poseidon Ocean. Their people liked that them. His kingdom was attacked by the forces of a ruthless king, Vector. Vector used Gorgonic Guardians to attack Reginald's forces. Reginald used mirrors to reflect the attacks of Gorgonic Guardians. Vector, then, sacrifices one of his man to Summon a water God, Abyss to combat. Then, suddenly, Reginald's friend, Dumon comes to save him from Vector and to fight. Rio rides a horse and arrives at the battle where she sacrifices herself to bring out another water God Crystal Zero.
Meeting with YumaEdit
Reginald was the #1's bully and tyrants to Yuma's school. When he provoked to be a real duelist dueled to the top of the other. After he defeated Bronk Stone, he took his deck and humbled mixed Yuma one. Shark wanted to give Yuma a chance to get his friend back in a duel with his most prized object of Yuma's on the line. As Yuma did not dare to, Shark took Yuma's key and broke it. Since Yuma but now could no longer give him his most prized object, Shark made him another offer. If Yuma were to defeat him in a duel, he would return Bronk's deck, but if he loses Yuma he'll surrender his deck.
During their Duel, Shark took out matched Yuma with his Pro-skills. He said to Yuma several times that he should give up but kept fighting. As duel continues, he's body was taken over by a foreign power. Shark then was able to summon Number 17: Leviathan Dragon, which he had not in the deck before. He made duel quickly worse and worse for Yuma to ask aid from Astral giving him his own Number to turn do over and defeat Shark. After his defeat, he accepted it and was, as promised, returned Bronk's Deck back.
After haven beaten by Yuma, Reginald no longer went to school for a while and avoided contact with people who knew him. Reginald was in the seedy gang of Scorch and Chills received and believed he had found a place where he belongs. He also called himself to quit dueling for good, but Yuma keeps challenging him several times. Reginald repeatedly refused and tried to escape from Yuma but Yuma's stubbornly pursued until he agrees and leaves the gang of Chills and Scorch. As Shark asks Yuma why he pester him all the time, Yuma explained that they are friends and he can't stop worrying about him. Shark then accepted the challenge with the condition that if he wins Yuma gives up his key. Shark took the opportunity to try out his anti-equal Number's strategy, defeating Yuma playing with this. Still, he let him and his followers wanted to be left only in peace.
A few days later, Reginald found out that Scroch and Chills each ones are obsessed by Number and intend to commit a museum robbery. When the two noticed that Reginald overhears them, they demanded of him that he should join them. Reginald agreed and thus drove them to the museum at night, but there stood before them alongside Yuma, who was informed by another member of the gang about how much trouble Reginald is in. Yuma had heard that the two brothers wanted to blame in shoes at the end and Reginald could not allow this. In order to stop Scorch and Chills, Yuma and Shark face them in a Tag-Team Duel. Scorch's and Chill's Number cards overpower Yuma and Shark. Shark, who notices Yuma's determination to not give up on him, entrusts Yuma with one card that turns the whole Duel around.