If you don't want to read the original 17,000 word AU post, see below the explanation of what's going on.
The premise was that the characters who canonically died in the Infinity Castle & Sunrise Countdown get to live, and vice versa, with the caveat being that Nezuko was not part of the battle so she gets to live (going by Anon's prompt). The Ask was about the aftermath so most of the AU is about the aftermath, but at this point in AU:
--Zenitsu died of his injuries from fighting Kaigaku, told Yushiro to go save the woman he loves
--Yushiro saves Tamayo by getting the secret!medicine from Kanao, changes Tamayo into a human against her will and gets absorbed by Muzan while saving her
--Inosuke saves Shinobu (scarring her face in the process) but dies fighting Douma
--Muichiro loses an arm in the fight against Kokushibo, but he and Genya are otherwise intact, and Sanemi dies after managing a few words to Genya
--After Muzan is defeated, Giyuu collapses and holds Tanjiro's hand, apologizes for being unable to protect him, and dies
--Himejima holds on (but falls unconscious), withstanding injury and the mark
--Iguro and Mitsuri are comatose and shredded, but they have all their limbs and are alive
--When Tanjiro changed, Muichiro noticed and fought him first, Genya and anybody else still standing tried to help, but ultimately Kanao saw that while he had still freshly changed, there was still a chance to stop him if his head was cut off at exactly the right spot
--But getting that shot meant Tanjiro had a better shot at her heart
And then in the aftermath of the AU, we followed a bunch of their interactions and wound up with:
--So many complicated feelings about what they've all been through (and like, how Tanjiro ended up a murderer)
--After going through a depressive episode, Shinobu has a renewed sisterly relationship with Aoi, to whom she gifted Kanao's butterfly hairpiece. Kiyo, Sumi, and Naho go to school like regular children, with Shinobu having rejected Tengen's offer to adopt them. Shinobu has prominent facial scars, wears Tamayo's hairpin, and extremely occasionally, Inosuke's mask.
--After some attempt at backing out, ObaMitsu survives and makes good on their promise. They assumed he totally lost his vision and she lost her womb, but neither ever asked for the medical details to be sure, so they are very happily surprised when it is revealed that he still has some vision (they can look forward to other happy surprises later). Also, Tamayo figured out how to treat The Mark, so yay.
--Muichiro, Genya, and Nezuko are handling things pretty well, all things considered. They more or less become sworn siblings (Senjuro, a literature fanboy, sort of fanboys over their bond). Nezuko wears Giyuu's (repaired but too big for her) haori and reads scraps of a book called "The Legend of Zenitsu" which a sparrow collects for her. Muichiro wears braids like Mitsuri used to because he finds it funny. He is of course not the one who braids his own hair. Genya has no style updates.
--Hear me out, but... I kind of wound up pairing Himejima and Tamayo?????? And I, who am not much of a shipper and generally only tend to go for canon pairings, really kind liked it????????????? Even though I otherwise would never????????? Like??? They have a son and his name is Chachamaru. Plus they pretty much adopted Muichiro, Genya, and Nezuko and they all live in the Kamado house. But if you asked them if they're a couple, they're like, "???? ew no ?????"
SO YUSHIRO IS PISSED BEYOND THE GRAVE, RIGHT!?
--Well, yes, at the very end
--Like
--I really, really liked the short conclusion I wrote that takes place in hell
--Basically like
--Yeah
--I loved it
--Hashira, and like
--Tanjiro, and pals, but like, Muzan, and, yeah
