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.
An alternate universe version of Rathie appears in Yu-Gi-Oh! ARC-V.
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.
In Yu-Gi-Oh! 5D's Tag Force 4, Yu-Gi-Oh! 5D's Tag Force 5, and Yu-Gi-Oh! 5D's Tag Force 6, Rathie sells Booster Packs to the player in his shop.
By giving him items, the player gets discounts on Booster Packs. The player can unlock the Lovey Dovey Deck pack in Tag Force 4; Picking Flowers in Tag Force 5; My Wife Plus Plus in Tag Force 6 by giving him each of the following figures; "White Magician Pikeru", "Ebon Magician Curran", "Dark Magician Girl", "Card Ejector" and "Cyber Tutu". These are the figures seen in his shop when he appears in the anime.