Rio is a character in Yu-Gi-Oh! Zexal and is Sharks sister. They are twins and are both from Barian world. They both are Barian Emperors and sent to Earth by Don Thousand. Her barian name is Marin and in the english version, her last name is pronounced Kastle. She is the younger twin of Shark and sided with Barian World, determined to follow her brother no matter what. Rio was absorbed by Vector after losing a duel to him, but was later revived by Yuma and Astral's duel.
Known as Marin, she was a priestess and a princess, sister to the king of The United Lands of The Poseidon Ocean who was known as Reginald (Nash) and was known on Earth as Shark. One day, their kingdom was attacked by Vector and his army., who had set Gorgonian Guardians to steal and loot on it with mirror shields. Vector offered a blood sacrifice to the ocean god Abyss, turning the battle back into his favor. Marin made a self-sacrifice and rode up Abyss and was grabbed. She was plunged into the sea to revive another god. This action was due to Don Thousand hypnotizing her.
Don Thousand influenced her death to aid his own revival.
After a number of unknown years,