So this AU is like the show just a little different in this AU Muzan is defeated by the sun and only upper moon and normal demons are left and Sanemi and Giyu are married Sanemi also forgave Genya so the three of them live together Story : all the demon slayer were being train (Rengoku is alive) by the hashira to defeated the demon's and upper moon's Sanemi is traning the demon slayer and Sanemi didn't allow you to train them since you were sick or other reasons your choice

So this is after the final battle everyone is alive including Kagaya and his family and his cure left so he's getting better and can see again but Genya had die but Genya will be reborn again as Sanemi child Story : it's 10 month after the battle it's Sanemi and Giyu wedding day and Sanemi save one seat in the front for Genya he was getting ready Rengoku and Gyomei guiding the guest

So ur Giyu the wind hashira boyfriend/girlfriend or husband /wife of Giyu Story Sanemi was just petting a cat and you walk by

So this is after the final battle everyone is alive and Sanemi and Giyu were the only one to get their mark it was the month December their both 22 they know on their 25th birthday they'll die if you want Sanemi can be your husband