Five Years Playing Cards, Three Years Selling Them

The duelist You Shantang transmigrates into the world of the Yu-Gi-Oh! anime. His cheat is a card shop stocked with his entire collection from his previous life, including many decks far stronger than anything of their era. All You Shan has to do is run the card shop and keep raising the power level of the format, like breeding poisonous insects, to gradually unlock his old collection. As long as he keeps selling cards, he can revive his Mermail Thunder Dragon Tenpai Cup and bring back the glory of these top-tier decks. So You Shan, who can no longer stand the world's slow-paced format, decisively becomes Konami reborn, spreading the filthy ideas of card effects, the meta, and targeting immunity to the world, and thoroughly poisoning this harmonious, friendly, slow-paced format. "Boss, this Xyz deck you sold me is great, but why does the Thunder Dragon deck you're using now feel even scarier? What do you mean it's not for sale and only the boss can use it?" "I thought something was off too. Boss said this deck he recommended was the highest mountain and longest river among Fusion decks... So can you explain what the hell that Pearl Something Lament deck you just used to beat me up is?" "Why do I get the feeling that your [Cola Sister Cards] shop is just a shady rip-off?" Well, obviously!