Rathie, known as Kurumizawa in the Japanese version is a shop owner in Yu-Gi-Oh! 5D's. His name is not mentioned in the English anime, but has been used in various video games.
Rathie helped Carly investigate the Crimson Dragon appearance at the Fortune Cup, by researching the Signers. Knowing Carly would want to contact Akiza Izinski, he also dug up information on the Arcadia Movement, which he wasn't willing to give her for free. To his delight, Carly gave him a rare "Dark Magician Girl" figure in exchange for the information.
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