Rio Kastle

Rio Kastle, known as Rio Kamishiro in the Japanese version, is one of the main characters, appearing in the Yu-Gi-Oh! ZEXAL anime. She is the younger twin sister of Shark.

Appearance
Rio has dark pink eyes and like her brother, she has pale skin and dark blue hair with light blue bangs. Rio also wears a ring on her right little finger, which was previously owned by her brother. Rio's appearance attracts many initial admirers, including Bronk.

Her attire includes a white jacket over a light purple shirt, black stockings, white skirt and shoes. The left coattail of her jacket has a conch-like ornament hanging down. At school, she wears the standard uniform, with hers being green due to her status as a second year student. She wears longer stockings than most female students. Her casual outfit is composed of a blue-white striped sleeveless T-shirt, a blue upper knee length skirt and white high-heeled sandals.

Rio's outfit in her past life was that of a princess. She wore a long hood on her head, white heeled sandals, a white dress and three gold rings on her legs. She also wore this outfit when she was possessed by Abyss.

Personality
Despite her appearance and previously spending a large amount of time in hospital, she is a confident and adamant person, getting annoyed when things do not go her way. This is usually shown when conversing with her brother. Her confident personality assists in her interests which allows her to conquer sports such as soccer, baseball, basketball and boxing with ease. Despite all of this, Rio also shows somewhat of a childish side as well, shown by her fear of cats (this showing she has ailurophobia) and calling Shark a "meanie" when he teasingly refused to help remove one from her sight. Rio tends to be annoyed when people refer to her as "Shark's sister" instead of calling her by name as indicated by Yuma due to her snapping at him when he continually calls her as such, and especially does not like it when someone insults her brother. This is further seen many times during her Duel against Aika as she got mad at her for making a rude remark about Shark.

Despite being occasionally irritated with Yuma for not addressing her properly as "Rio", his personality and playful antics makes her let it slide given that she is thankful to him for helping her brother and being his friend. It is also revealed that she goes very far on things and acts strong because she feels she has to or people may use her as a shield against her brother. She later shows admiration towards Yuma and Alito as she commented they have amazing Dueling spirit.

She takes great pride in her abilities and effort as she has no problem in showing them when people underestimate her as she believes women are not to be viewed as "pretty decorations".

Rio also has a empathetic quality to her personality as well. This is demonstrated when she finds Bronk injured on the way to school, and shows genuine concern to him and helps treat his injuries.

Abilities
Rio possesses the ability to sense Barians. This is shown when Girag arrived on Earth, which caused her great pain and she foretold that "they" were coming to take "the most important thing".

When Mizael arrived later, Rio went into a trance-like state and again said that someone was coming to destroy "the most important thing" and then describing a dragon of ill omen that would destroy everything. She once more senses the presence of the Barians, and reports that they are attacking Yuma.

During those moments, Rio enters some sort of trance while a mysterious red or green aura appears around her.

After boarding the Different Dimension Airship, Rio was able to see Astral. She expressed surprise that she could then still do so after leaving the airship.

Past life
Rio was once the ruler of the United Lands of the Poseidon Ocean alongside her brother. One day, the kingdom was attacked by Vector, who led a fleet of ships and several "Gorgonic Guardians" to lay waste to it and loot it. After Reginald led the kingdoms forces to defeat the Gorgonic Guardians with mirror shields, Vector performed a blood sacrifice to the ocean god, Abyss, turning the battle back into his favor. Rio rode up to Abyss and was grabbed. She offered herself as a sacrifice, plunging into the ocean depths to revive another god. She and her brother were both eventually reincarnated.

Current life
As children, Rio and her brother, Reginald, lived in a mansion with their parents, where he taught her how to play Duel Monsters. One day, Rio stole Reginald's Deck as a prank, forcing her brother to chase her for it. They accidentally knocked down a suit of armor, which nearly fell on Rio. Reginald saved her from being crushed, only to acquire a scar on his back. Reginald and Rio were also involved in a car accident that, according to Kurage, killed all of the Kastle family members, including Rio herself and Reginald, but they somehow survived. At another time, Rio and Reginald visited a theme park where the former offered the latter one of two rings which they both could wear. Reginald initially refused to wear his ring, causing Rio to throw them on the ground and walk away in anger.

Rio once Dueled Quattro who was operating under the orders of Vetrix. He played the Spell Card, "Flaming Hell Blessing", which set the surrounding area on fire. She was critically injured in the blaze, though Quattro carried her to safety, his face being scarred in the process. After this, Reginald began wearing both of the rings from their childhood to remind himself of her.

In order to help his sister, Reginald entered the National Duel Circuit and made it to the final match against Quattro. In the break room, Quattro set his Deck up to fall on the floor, causing Reginald to see some of its contents. This caused him to be disqualified.

Barian Invasion
Even after the World Duel Carnival, Rio was still in the hospital, albeit with only bandages covering her eyes. Rio felt Girag's arrival from the Barian World, which caused her pain. Because of this, Reginald (who by now often used "Shark" as a nickname) arrived later along with Yuma and Tori after him being called by the hospital as well as sensing Rio's pain. During that time Rio blurted out that someone is coming to take the most important thing, which worried Yuma as he had heard something similiar before.

Shark visited Rio at hospital again and gave her one of the rings from their childhood. She was later abducted by Chitaro Ariga, who was following Gilag's orders and was imprisoned in a cage within Sentaro's manga book. Sentaro approached Shark and informed him of this, causing them to Duel. When Shark attempted to use "Zeus Breath", Sentaro claimed that the manga world be destroyed if he lost - with Rio still inside it.Yuma and Rei Shingetsu went to Sentaro's manga writing room and managed to find several pages detailing how the Duel would go, as well as the result, which resulted in the death of both siblings. However, Shark called out to her and their bond managed to shatter her imprisonment, making her appear on top of a tower on the "Comic Field" Field Spell Card. When her bandages are blown off of her face, she insulted Shark's Dueling skills. After the Duel, she collapsed and was carried away by Shark.

After her recovery, Rio was able to return to Heartland Academy. On her first day back, she intended to go with her brother, but he ran ahead without her. When she found him, she called him a jerk and told the gathered students he could never do anything without her. She ate lunch on the roof with her brother, Yuma and his friends. She spoke with Yuma, realizing he's the one who beat her brother earlier but believed him to be Kite. When she found out who he really is, she recalled his catchphrase and then mispronounced it and is annoyed when Yuma refers to her as "Shark's sister". Their lunch is interrupted by a group of students representing various clubs, including Yata-Garasu. They wanted Rio to become their manager.

She agreed to visit each club, but would only join if they defeated her in the club's activity. By herself, she defeats the school's soccer team and various other clubs, chiding them for asking her to manage them when they can't play. She said that she had to be strong, as she didn't want anyone to use her weakness to get to her brother. She is then approached by members of the Ikebana Club, who invite her to join them. When they arrive, they are introduced to Aika Hanazoe, the club's leader. The entire club had been hypnotized by Gilag and Aika put everyone to sleep. However, Yuma and Rio were both able to resist (and unbeknownst to either of them, Rei Shingetsu as well). Though she intended to Duel Yuma, Rio stepped in and challenged her instead. Despite her use of a "CXyz", Rio countered her moves and defeated her with "Ice Beast Zerofyne". Yuma then nearly called her "Shark's sister" again, but accidentally called her "Shark's brother" instead. Though initially annoyed, she eventually laughed and told Yuma that she had heard that her brother had changed a lot when she was in the hospital. However, he went back to the way he was because of Yuma. As the group walked home, Rio saw a cat and hid behind her brother, frightened.

Rio participated in the "Sports Duel Tournament" held by Yuma and his friends, where she ended up on a team with Bronk. They would be defeated by her brother and Yuma during the Volleyball Duel, but they defeated Tori and Cathy in the Wrestling Duel. Afterwards, she complimented the two on their plays. Sometime later, Rio went shopping with her brother. There, she sensed Mizael's arrival on Earth and commented about a horrifying dragon. Knowing it to do with the Barians, they hurried to where Yuma was Dueling inside a Sphere Field generated by a Barian's Sphere Cube. Rio watched the rest of the Duel, which Kite eventually took over for Yuma. She looked on in horror when her brother attempted to save Yuma from his fall and ended up falling down the cliff himself. She visited her brother in the hospital while he was recovering. One morning while talking to Tori at school, Rio sensed that Yuma was in danger, therefore she, Tori and Shark rushed to aide Yuma and Rei at the Heartland Pier where they entered a Battle Royal. After they managed to defeat several Duelists, Gilag intervened, forcing all of the brainwashed students to attack Yuma, however Alito intercepted, using a combination of "Lightning Clinch" and "Brain Reboot" to defeat the remaining Duelists. Rio then watched as Yuma began his Duel with Alito in the Barian's Sphere Cube.

Later at school, Shark was asked by Bronk to Duel him, who was trying to gain his blessings to date Rio but Shark declined since he was no match for him. He also added that Bronk was not even at Yuma's level, causing Bronk to jump to the conclusion that Rio was with Yuma. Flip and Caswell overheard this and spread a rumor around the school. Oblivious to the misunderstanding, an angry Rio challenged Shark to a Duel. During the Duel, Shark was able to counter every strategy Rio played and voiced little faith in Rio's confidence as a Duelist. While Shark was proud that Rio was able to gain courage, he proclaimed that she still has a long way to go if she wanted to beat him and defeated Rio with his "Shark Caesar". Afterwards, Shark learned the rumor from Rio and cleared up the misunderstanding, clarifying that he was not the one spreading the rumor. Bronk then asked to Duel her one day and began to ask something in regards to what would happen if he won, but trailed off. Rio said she'd look forward to it. Upon finding out that Caswell and Flip had spread the rumor, Rio chased them down out of anger.

During Heartland Academy's Cultural Festival, Shark observed the play Rio was acting in and displayed irritation watching her with Yata-Garasu. When Bronk came to him, Shark was shocked by his cosplay as "Gogogo Golem" and grew annoyed that he was calling Shark "brother." Shark's irritation prompted Rio to throw her shoe at Shark and tell him to be quiet. After hearing about the Different Dimension Airship giving Yuma, Shark and Kite access to the Barian World, Rio forced Shark to let her join them, surprising Yuma. During the trip, an array of monsters begin assaulting the ship. Seeing this, Rio and the others went to the exterior, using their ace monsters to battle with them. After this, the ship was sucked into a portal, transporting the group to "Sargasso the D.D. Battlefield" where she and Bronk supported Shark during his Duel with Dumon. Rio and the others returned to Earth after Vector's defeat.

Legendary Number War
When Vector awakened Don Thousand, Rio was able to sense it. She, Yuma, Tori and Shark were brought into the Different Dimension Airship by Astral, who showed them a message from Kazuma Tsukumo to gather the seven Legendary "Numbers". On the way to the first location, they crashed into Dumon, who was also headed to the same location they were, teleporting them all to a jungle. Rio and Tori were then separated from the rest of the group, having run into snakes at a temple, which were later fended off by Yuma and Shark. She later watched Yuma's Duel against Mach.

Rio later accompanied her friends to Number 65's Ruins, where she was trapped in a cage and watched Astral's Duel against Number 96: Dark Mist. After the Duel, Rio and the others were able to escape the collapsing ruins with the help of Kite Tenjo. Rio also came to Spartan City in search for Number 54's Ruins. Before that, she and Tori came back from shopping, which annoyed Yuma and Shark. She was also present for Yuma's and Dextra's Tag Team Duel against Alito and Nistro. When the group arrived at the bottom of the mountain leading to Number 46's Ruins, Rio chose to stay behind along with Tori because she claimed that "girls don't climb mountains".

Later, Rio saw a vision of herself falling off a cliff and being chased by Vector. She was contacted by Abyss, who possessed her and forced her to jump off the airship and into the ocean. When Shark arrived to save her, Abyss began a Duel with him, during which he showed Shark visions of their past lives. Eventually, Abyss released Rio, causing her to fall a great distance as Abyss insisted that Shark would lose his sister in this life just like in his past one due to the weakness in his heart. Rio was caught by Yuma, which allowed Shark to contact "Number 94: Crystal Zero the Polar Ice Princess" and use it to defeat "Number 73: Abyss Splash the Roaring Waterfall Deity". The group was transported out of the ruins and back to the airship after this, but Rio remained unconscious. Rio was returned to the hospital to recover. When Shark visited her one day, she had another premonition and told Shark that a great darkness was surrounding Yuma and that a great tragedy would soon happen.

Rio's room in the hospital was broken into by Kurage, who infected her with jellyfish poison in order to lure out Shark. However after Shark and Quattro were able to defeat Kurage in a Duel, both siblings were cured. After his defeat, Kurage revealed Shark's and Rio's deaths on the day of the car accident to the former.

Reginald Kastle
Shark and Rio are twins and share a strong bond ever since they were children, symbolized by matching rings that Rio obtained.

Following Rio's Duel with Quattro, in which she was critically injured and wound up in a hospital bed wrapped in bandages, Shark dueled in the National Duel Circuit for her sake but pressure escalated to such an extent that he peeped at his opponent's Deck before the final match, an action that caused him to be disqualified and banned as a result. During the time Rio was in the hospital to recover from her injuries, Shark often visited her.

Despite their bond, Shark has a typical tenuous "brother-sister" relationship with Rio, irritating one another and having normal siblings squabbles. If these squabbles escalate, they settle them through a Duel and have done so a total of one hundred times.

Bronk Stone
Bronk is one of Yuma's friends, and as a result is also an acquaintance of Rio. However, Bronk has a crush on Rio, which he developed when he saw her return to Heartland Academy. This infatuation developed further when Rio helped him with an injury on the way to school. From that point on, he had been trying to develop a relationship with her, and actually asked Shark for his permission to ask her out. However, Shark refused and this actually led to a clash of the siblings. From this point on, Bronk has made no significant moves toward and they remained friends. However he later started calling Shark "big brother", pretending he was his brother-in-law.

Tori Meadows
Rio and Tori talk on friendly terms and are shown to be kind to each other. Once Rio was out of the hospital, on her first day of school she ate lunch with Tori and her friends. Tori looks up to Rio, even asking her to teach her Dueling one day. She also tagged along with Tori when they attempted to travel to the Barian World and both cheered on their friends in their Duels.

Past Deck
Though no cards in her past Deck were shown in-Duel, a flashback showed a few of them outside of one. Shark helped Rio construct this Deck when they were both children.

Barian Invasion
Rio plays an Ice Deck featuring WATER Winged Beast-Type monsters. Rio is also shown to be able to shift strategies easily, utilizing burn cards such as "Blizzard Falcon" and "Diamond Dust".

Legendary Number War
While under the control of Abyss, Rio uses a "Gorgonic" Deck focused on ATK reduction.