>>50440128The original premise for Yu-Gi-Oh was that the Pharaoh was just an evil spirit that liked tormenting people with various games, some of which you'd be likely to play in your daily life.
Eventually they made the chapter that introduces Seto Kaiba and the game the Pharaoh plays with him is a card game rip off of MtG and DnD.
They'd go back to different weekly games after that but the fan reaction to the card game chapter was so strong that they eventually brought back Kaiba as the final boss alongside the game, and then made a sequel manga that focused on JUST the card game (this is the manga that would eventually get adapted into the anime most people watched).
Despite all this though it would take a while for the card game to actually become a thing in real life, thus no part of the manga actually has any concrete rules and it's mostly bullshit DnD for a majority of it.
The same thing happened with the first season of the anime, it wouldn't be until the anime's second season that the card game actually became a thing and they incorporated the rules into the show (and even then it would still be pretty iffy for a while until GX)
