Rio Kastle

Rio Kastle, known as Rio Kamishiro in the Japanese version, is a character 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 purple 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 seems to attract many initial admirers, including Bronk.

Her attire includes a white jacket over a light purple shirt, black stockings and white shoes. At school, she wears a green female uniform.

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, allowing her to conquer sports such as soccer,baseball, basketball, and boxing with ease. Despite all of this, Rio is extremely terrified of cats.

Rio tends to be annoyed when people refer to her as Shark's sister instead of calling her by her name, and especially does not like 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 Reginald or snapped at Yuma as he continually called her "Shark's Sister". However, Yuma's usual antics makes Rio let it slide given that she is thankful at Yuma for helping her brother and to accept him as a friend.

Abilities
Rio has some unknown connection to the Barian World and its people. She can sense their actions like when Gilag when he appeared in the human world, which causes her some pain.

History
As children, Rio and her brother Reginald were visiting a theme park where she offered Reginald one of two rings which they both could wear. Reginald initially refused to wear it 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 a card, "Flaming Hell Blessing", that 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, Shark 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.

Yu-Gi-Oh! ZEXAL II
Even after the World Duel Carnival, Rio was still in the hospital, albeit with only bandages covering her eyes. For some reason Rio felt Gilag'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 worries Yuma as he knew what Rio was talking about.

Shark visited Rio at hospital again and gives her one of his rings which were given to him by her when they were younger. She was later abducted by Chitaro Ariga following Gilag's orders and is imprisoned in a cage. Sentaro approached Shark and informed him of this, causing them to Duel. When Shark attempted to use "Zeus Breath", Sentaro threatened to harm Rio if he activated it. Yuma and Rei Shingetsu go to Sentaro's manga writing room and manage 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 manages 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 collapses and is carried away by Shark.

After her recovery, Rio is able to return to Heartland Middle School. 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 speaks with Yuma, realizing he's the one who beat her brother earlier, but believed him to be Kite. When she finds out who he really is, she recalls his catchphrase and then mispronounces 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, who want 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 he 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 the 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 "Chaos Xyz", Rio countered her moves and defeated her with "Sylphine, the Cold Bird Beast". Yuma then nearly called her "Shark's sister" again, but accidentally called her "Shark's brother" instead. Seeing Yuma's usual antics makes her laugh instead, also Rio says to Yuma that she had heard that her brother had changed a lot when she was in the hospital. However that he went back to the way he was because of Yuma. As the group walks home, Rio sees a cat and hides behind her brother, frightened.

Deck
Rio plays a Ice-themed Deck featuring WATER Winged Beast-Type monsters.