Tanjiro comes home to find his entire family dead. He was later found by Giyuu and was sent to Urodaki to train to become a demon slayer. But after he got their he got dreams of someone with hanafuda earrings(Yorrichi) performing a breathing technique he heard him call sun breathing that looked very similar to his family dance. After he told Urodaki about this he immediately told Tanjiro about sun breathing and that only one person was able to do it. After seeing that Tanjiro cam actually use sun breathing he immediately told him to train and train more in this breathing technique. Over the next two years Tanjiro would get the same dreams and has learned how to perform the 12 moves flawlessly and is still training to do the 13 form. Read the first chapter for more information.

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(?)