I don't own any varieties of Pokemon or any varieties of Yu-Gi-Oh!
In this story Yu-Gi-Oh! is set in the past, Yu-Gi-Oh! GX is set in the present, and Yu-Gi-Oh! 5D's; Yu-Gi-Oh! Zexal; and Yu-Gi-Oh! Arc-V are set in the future with Yu-Gi-Oh! Zexal being farther in the future than 5D's and Yu-Gi-Oh! Arc-V being father in the future than Zexal.
Xx was sleeping in his bed in his room in Vaniville Town in the Kalos region after stopping an evil person tried to conquer the Kalos region with Dialga, Palkia, and Giratina when Arceus appeared in his dreams. He asked, "What's with the visit? The Alpha Pokemon told him that because he was hit by the Temporal, Spacial, and Renegade Pokemon he losing his ability to stay on this world. Arceus also said that he was going to sent the camouflage clad Pokemon trainer to an alternate world but he wasn't going to send Xx to an alternate Pokemon world because he believes that he should try something different but still with monsters but instead of Pocket Monsters they are Duel Monsters and the Alpha Pokemon decided to do something to give the Pokemon trainer something more familiar as he handed Xx a Duel Monster card in gold metallic print on the top of the card was Pokemon "Number 652 Chesnaught". The Alpha Pokemon stated that there will be 807 different different Pokemon from Bulbasaur to Zeraora as well as different varieties of certain Pokemon, that he will teach him the rules, Xx could communicate with them, giving him a licence for a duel runner, turn his bicycle imake him a duel disk, and that there are some prejudice in that Xx could stop. Xx agreed with Arceus' ideas and reasoning. Arceus said, "Let's get started."
Arceus turned Xx's bicycle into a duel runner, created him a licence, taught him the rules for both ground dueling as well as turbo dueling, taught how to ride a duel runner, made the cards, how to communicate with said cards, made him a duel disk, and what prejudices exist there. After about three months Xx was ready so Arceus sent him to a Yu-Gi-Oh! world but because of the temporal powers of Dialga it would be easier for Arceus to send Xx to either the past or the future. The Alpha Pokemon decided to send him somewhere in the future.
Xx landed in New Domino City the first thing he decided to do was to get a job. The job he ended up getting was that he had to watch over a pair of rich kids in the Tops District because their parents are very busy. Xx was glad he's good with kids and hopes that they aren't rich brats that will actually listen to him. He decided that he'll have to see for himself. It turns out that the kids' names and personalities are the excitable Leonard who prefers Leo and the calm and collected Luna plus they weren't rich brats they're just rich kids with personality.