"Where am I?" After the defeat of Muzan and live his entire life, he expect to see his family's and friends. But, when he open his eyes, he see's a new world. Demon Slayer and Genshin Impact are not mine and belong to their respective owners.
Instead of Giyuu tomioka finding Tanjiro, kyojuro Rengoku, the flame hashira, does. Kyojuro see's potential in Tanjiro and because he has no successor he trains Tanjiro in the art of flame breathing. Nezuko will be dead(by tanjiros hands). Sorry not sorry(?)