Tanjiro, Nezuko, Zenitsu, and Inosuke travel to Tokyo because their mission to slay lots of demons. Meanwhile, they meet Deku and the others, what would happend if they meet one each other?

Last Giyuu remembered was that he and the other remaining pillars as well as Tanjiro and the boy's friends were fighting Muzan along with a mysterious Upper moon that they didn't know existed. To attain victory he sacrificed himself to take a blow from uppermoon directed to Tanjiro. But how was it possible that he was now looking at the concerned and mildly shock face of his long dead best friend, Sabiro. //A convenient attack from an OC Upper moon sends Giyuu into a parallel world where he was the one that dies and Sabito survived. A fic where every pillar is alive// -Is inspired and greatly base by the story 'Blue' by KuriKuri on Archive of Our Own-