Reginald Kastle

Reginald Kastle, known as Ryoga Kamishiro in the Japanese version and nicknamed "Shark" in both versions, is one of the main characters in Yu-Gi-Oh! ZEXAL and is one of Yuma Tsukumo's friends and rivals. He was originally a cold and malicious person but has grown quite humble.

Appearance
Reginald has dark blue eyes, pale skin and dark purple hair, which resembles tentacles hanging down, referencing his Deck theme of aquatic creatures. His accessories include a grey, shark tooth-shaped pendant, and two grey rings on his right hand. He also owns a grey and green Duel Gazer with a red lens and a yellow spike. In the manga, he also wears a large red jeweled, yellow pendant that vaguely resembles a spaceship.

His attire includes a dark purple jacket over a black shirt and dark pants. When in his school attire, he wears a white shirt with green-lined sleeves, tie and a collar. During his National Circuit days, Reginald wore a white top with a purple waist coat and his usual dark pants.

Personality
After being disqualified from the National Duel Circuit for trying to look at the another competitor's Deck, Reginald became bitter and uncaring, the way he held himself at the beginning of the series. Cold and malicious, Reginald flaunts his power by taking the Decks of the people he defeats, making them squirm in the process, such as when he defeated Bronk Stone. When he became possessed by the "Numbers", he became quite violent, destroying the scenery surrounding him throughout the Duel.

However, he does have some honor; as he returned Bronk's Deck upon losing to Yuma as he promised and keeping all the Decks he'd stolen from people completely intact. His defeat to Yuma seems to have humbled him in a way - he is no longer overly cruel to people, as shown when he returns Yuma's pendant after winning an Ante Duel with it at stake. He also seems to put more faith in bonds and friendship, shown by his willingness to form a team with Yuma during the Tag Duel with Scorch and Chills. He further entrusts Yuma with a card that would allow them to win the Duel.

Reginald also tries to rescue The Emperor's Key from Kite and Orbital 7 when it is stolen, clearly stating that he sees Yuma as his friend. In the Duel with Kite, Shark remembers Yuma, and that Yuma would never give up. Before Shark's loss to Yuma, he hated people who never gave up.

After learning from IV that he set him up to be disqualified and hurting his sister, he entered World Duel Carvinal and became more cold and more brutal to any duelist he challenge and even considering his friend Yuma his enemy.

Reginald's friendship with Yuma has also helped him in handling the "Numbers" cards. When "Number 17: Leviathan Dragon" came in contact with him, it easily took hold of him. However, he was able to fight off the influence of "Number 32: Marine Biting Dragon - Shark Drake" because of his bond with Yuma, making him the first known person to be able to resist the influence of the "Numbers "without a special item or power. Despite being able to initially resist the influence, Tron said that it did infect him and it will amplify his darkness caused by his desire to take revenge against IV.

Reginald holds an intense hatred towards IV for setting him up to be disqualified and implying that he hurt his sister intentionally.

History
In the past, Reginald was a well-known and popular Duelist within the National Duel Circuit. The pressure got to Reginald's head, causing him to become desperate because he wanted to support his sister, who was in an accident being heavily injured. While preparing for the finals and in the waiting room, he noticed that his opponent, IV dropped and left his Deck. While not intentional, Reginald's desperation got the better of him and ultimately looked at the visible cards on the floor. Midway through his Duel, while neither Duelist had a visible advantage, Reginald was disqualified and the match canceled, as he was found out to have looked at his opponent's cards. This also caused him to be permanently banned from the Duel Circuit.

After this ban, Reginald turned into a delinquent and began to steal the Decks of his opponents once he beat them. It is known by most students within Heartland Highschool that Reginald was not only a skilled Duelist, but also a bully. He obtained the nickname "Shark", due to the fact that he used an ocean-themed Deck and because he ripped his opponents' Decks out of their hands swiftly and with malice. Despite Reginald's actions, Yuma defended him, as he believes that everyone has done something in their past which they regret.

Yu-Gi-Oh! ZEXAL
Shark defeated opponents at his school, taking their Decks after they lost. After defeating Bronk Stone he met Yuma Tsukumo, who attempted to defend Bronk. When asked what his most important thing was, Yuma told him it was his pendant. Shark ripped the pendent from his neck and throws it away. Shark challenged him to a match, with both Yuma's and Bronk's Deck on the line. Yuma accepted.

They Dueled in the city square, with Shark quickly gaining an advantage with "Big Jaws" and "Aqua Jet". He cornered Yuma, but then the "Numbers" were released from the door. Shark was possessed by "Number 17: Leviathan Dragon", which he proceeded to Xyz Summon. As the Duel progressed, Shark began to toy with Yuma, taking his Life Points down to a small fraction. However, Yuma managed to come out of this with the help of Astral, and managed to defeat Shark with his "Number 39: Utopia" at 5000 ATK, which knocked Shark out. When Shark awoke, he gave Yuma Bronk's Deck, keeping his promise. Shark said that Yuma was different than everyone that he has faced before and walked off without another word.

Sometime after the Duel, words of Shark's defeat spread around school and his reputation dropped. Eventually he stopped going to school and also quit Dueling. He was taken in by a gang led by Scorch and Chills, who hung out at an abandoned arcade. One day, while Yuma was late to school, Shark ran across a crossing and nearly hit Yuma while he was on his motorcycle. After Yuma is belittled by his friends who believe that his victories over Shark and Flip were just because of his "Numbers", he decides to find Shark and challenge him to a rematch, without using the help of Astral or his Numbers.

When Yuma found Shark, he refused to Duel as his previous loss to Yuma caused him to give up Dueling. Scorch and Chills nearly hurt Yuma and his friends, but Shark told them to stop, saying he knows them. Yuma proceeded to chase Shark and annoy him by requesting a Duel until he accepted. Yuma bet The Emperor's Key on the result. Yuma did not use his "Numbers" and Shark told him to do so, believing a victory over Yuma without "Numbers" would be meaningless. Yuma Summoned "Utopia", which Shark weakened with "Friller Rabca". This let "Black Ray Lancer" negate its effects and destroy it, which impressed Astral. Shark won with a direct attack from "Submersible Carrier Aero Shark". Shark took The Emperor's Key, but threw it on the ground as he walked off, telling him Yuma not be bother him again.

Shark soon overheard Scorch and Chills' plot of raiding the Heartland museum in hope of trying to steal a valuable Deck containing "Chaos End Ruler -Ruler of the Beginning and the End-". He also discovered that both thugs were possessed by "Numbers". When Chills and Scorch found Shark listening on their plan, he was forced to go along with them. Before going, he tells another gang member, Weasel, to run so he doesn't become involved in the dangerous raid. Weasel went and warned Yuma of the situation instead. Upon arriving at the museum, he found Yuma standing in their way, not allowing them to pass without beating him in a Duel first. He was shocked when Yuma bet his "Number 39: Utopia" on the Duel. Shark warned Yuma not to be concerned for him, but Yuma said he won't leave him alone to rob the Deck. Yuma also pointed out that Scorch and Chills were using him, and that their hideout is not a place for him to stay plus both Yuma and Shark are comrades. Shark then decides to Duel with Yuma against Scorch and Chills in a 2-on-2 Tag Duel. On his first move, he Xyz Summoned "Submersible Carrier Aero Shark" and managed to deal effect damage to Scorch. Scorch Xyz Summoned "Number 61: Volcasaurus" and activated its effect, which destroyed "Submersible Carrier Aero Shark" and dealt Shark damage equal to the ATK of "Aero Shark".

Having all their moves countered and with the appearance of "Number 19: Freezerdon", which gave "Volcasaurus" its Overlay Units back, Shark and Yuma were pushed into a corner. After Summoning "Utopia" and having it prevented from attacking by Chills' "Avalanche", Yuma used its effect to protect Shark from attacks which would have caused Shark to lose. After having "Utopia" and the newly Summoned "Black Ray Lancer' destroyed by "Volcasaurus" (avoiding losing by "Damage Diet"), Shark narrowly avoids losing from a direct attack by using the trap "Final Offering", ending the Battle Phase and giving Yuma "Armored Xyz". After eliminating Chills by forcing him to use his "Compensation Exchange" Trap, which saved "Volcasaurus" by taking damage equal to its ATK, Yuma used "Monster Reborn" to bring back Shark's "Black Ray Lancer" and equip it with the "Armored Xyz" Shark had entrusted to him earlier. It allowed him to give "Lancer" the properties of "Utopia", letting it destroy "Volcasaurus" and attack directly for the win. Afterwards, Shark comments that his card was able to improve Yuma's game, allowing him to keep it before smiling and walking off.

When Tori was trying to ask people about the "Number" cards, she ran into Shark, who told her that she should not get involved with those cards and that they are things that neither of them should understand in detail. Later, Orbital 7 attempted to steal the Emperor's Key. Shark retrieved it and was chased around the school by the robot. Just when Orbital 7 was about to kill him with a drill, Kite Tenjo stepped in and called a halt. Shark and Kite both chatted a little then a Duel started. Shark was confident about his Deck's new Anti-Numbers strategy which proved effective against Yuma. However, he still wanted to have a "Number", so he planned to steal Kite's "Numbers", but Kite noticed it and used "Number 30: Acid Golem of Destruction" so that its negative effects damage Shark when he steals it. Shark remembered that Yuma would never give up, grasped the key and continued the Duel. When Shark lost, he apologized to Yuma being that he failed to protect the Emperor's Key. His soul was taken in by the Photon Hand and he aged considerably. However, Kite was surprised that the soul didn't possess a "Number" card. He absorbed the soul when Yuma and his friends stepped in. Shark was then maintained in the hospital, being look after by Mr. Kay. After Astral and Yuma drew with Kite, he decided to release Shark's soul as he wasn't a "Number" controller. He awoke in the hospital afterwards.

At the beginning of the World Duel Carnival, he met Yuma who was panicking because he didn't have a Heart Piece. When he was asked if he would be participating, he replied he didn't feel like it. When he drove down the road a bit further, he caught a thrown "Mirror Force" card, the card that Shark associated with his ban from the National Circuit, and it turned out to be IV, his opponent in his last pro Duel. IV explained he purposely put his Deck where Shark could see it, to get him disqualified. IV also revealed that at that time Shark was not only affected by the pressure of the Finals, but also because of a promise he made to his sister who had an accident and was hospitalized, so he was easily tempted to look at IV's Deck, IV also says that maybe his sister's accident was not really a coincidence. Infuriated, Shark demanded to Duel with him again, but IV tells him to wait for the WDC and tosses him a Heart Piece, and leaves. Shark then decided to participate after all, to get his rematch with IV. He fell into IV's trap again as Tron told him to force Shark to participate in the carnival, probably because they want him to help them collect the "Numbers".

After Kari Tsukumo ordered Yuma to find Charlie McCoy, he overheard a crowd cheering. Knowing that it would be a Duel, Yuma ran over to see Shark defeat an unknown Duelist with "Submersible Carrier Aero Shark". After the Duel, Yuma congratulated Shark and asked him why he had decided to enter the WDC. Shark told Yuma about how IV had mistreated his sister into the hospital to trick him into being kicked out of the nationals, and now he wants a rematch with IV, but after that, he will quit the WDC. Shark tells Yuma not to get involved with him and then wandered off, vanishing from sight of Yuma and Tori.

During the second day of the WDC, after IV defeats Bronk and Caswell in a Battle Royal Duel, Shark charged into the area on his motorbike, asking him if he remembered the face of his "Number one fan". IV appeared amused, and leaves in a cloud of dust. III snares Shark with his Duel Anchor, preventing him from chasing after IV. In the proceeding Duel, Shark takes control of III's "Number" monster, "Number 32: Marine Biting Dragon - Shark Drake". The "Number" pierced his claws into Shark's chest, but Shark's strong will overcomes the power of the "Number" and he uses its power to defeat III. III told him to keep the card and gave him a Heart Piece, revealing that he himself already had a completed heart. Although he was able to withstand the "Numbers" by remembering his time with Yuma, Shark still wants his revenge against IV for his sister, which allows "Shark Drake" to infect Shark with a small virus that will amplify that darkness even further. According to Tron, this will help them with their plan to recruit Shark to their side.

When Yuma, Tori, and Astral were looking for Hart Tenjo, Shark saw them from the road above them and stopped. He overheard Yuma calling out for Kite with his D-Gazer. Shark continued to collect Heart Pieces, brutally defeating many Duelists as the power of "Number 32" began to exert its influence on him, fueling his desire for revenge even more. He was confronted by Yuma, who let Shark take his anger out on him in a Duel. Realizing this, Shark eventually came to his senses and cancelled the Duel.

Decks
Shark plays a WATER Deck consisting of monstrous looking sea creatures such as various races of sharks. He utilizes a Burn strategy in order to quickly gain the advantage through cards such as "Submersible Carrier Aero Shark" and "Explosive Urchin", with a focus on using Level 3 monsters to Xyz Summon Rank 3 Xyz Monsters.

Shark uses cards that can counter "Numbers", whether that be negating their effects with "Black Ray Lancer" or taking control of them with "Splash Capture". As his Xyz Monsters are Rank 3, their ATK tends to be on the lower side. He includes cards to decrease the ATK of his opponent's monsters such as "Needle Sunfish" and "Friller Rabca" to make up for this. A cautious Duelist, he includes many cards to counter Spells and Traps, such as "Deep Sea King's Judgment", "Mystical Space Typhoon", "Plate Salvage" and "Skull Kraken".