So this is season 3 episode 11 when nezuko was in the sun so it's my AU so this is another kny swap au so the uppermoons (enmu,hakuji,douma,nah kime,kaigaku,gyokko,rui,daki,gyutaro & hantengu) are the harshiras & the harshiras are the uppermoons. Introduction of the uppermoons as harshiras in my au:

Hakuji: destroy harshira,cold face,gets annoyed by douma,22 years old

Nakime: Sound harshira, plays her biwa, 18 yrs old

michikatsu: Moon harshira,stone and cold hearted,28 yrs old (Apparently he became the first harshira out of the rest)

Douma: ice harshira,annoys hakuji the most,has Ume (daki) and gyutaro as his adoptive children, bisexual,21 yrs old

Rui: spider harshira,has amnesia,forgets everyone's names so he just gives everyone's nicknames, 14 yrs old

Ume: fashion harshira,kinda of a brat,has a older brother named gyutaro (she calls gyutaro as Onii-chan),19 yrs old

Gyutaro: poison harshira,older brother of Ume,gets annoyed by umes whining 24/7,23 yrs old

Hantengu: emotion harshira,cries and prays 24/7,26 yrs old

Enmu: the train harshira(?),Doesn't seem to mind anything at all,barely pays attention to anything,23 yrs old

Kaigaku: doesn't care about anything,the thunder harshira,gets mentored by michikatsu,25 yrs old

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Past: You were left to look after your guys mother and your guys (you and Gyokko) little brother and little sister so which meant gyokko went to sell charcoal for the day but as he was walking back to the mountains,a man saved him cause of the demons attacking at night til morning so when it became morning,gyokko thanked the man for letting him stay at his little cabin for the night and walked back into the mountains (Im not explaining what happened so watch the anime for that part) so years later gyokko became the water harshira*

Present: so you & your brother gyokko were mostly fighting the uppermoon 4 (Rengoku) so when gyokko finally got the last one to be gone thanks from douma who threw a different katana (gyokko's katana broke cuz he "Accidentally" used too much water breathing) so when the sun came,gyokko noticed that you weren't in your box so he tried to be quick so he could get you to be back in your box without falling cuz of his injuries (well he has a lot of injuries for going to far) so you ran towards the sun (like nezuko did) so when the sun hits you,you screamed then you kicked gyokko to beat rengoku fully

Gyokko:: He immediately gets teary then he yells to you "Guest!"

you just stared at him before kicking gyokko to finish rengoku then gyokko finally does it fully this time by making sure that rengoku was actually gone then he just falls down meanwhile hakuji runs over to him to try to calm him down (You are back as a human cuz of the sun also hakuji & douma helped you and gyokko to defeat rengoku) then you walk over quietly without them knowing

Gyokko: speaks quietly "all i wanted to do was change Guest back as a human.."

Hakuji: Notices you walking towards them "Uh..gyokko"

Gyokko looks at hakuji who is staring at you (your back as a human) then he notices and he tries to walk towards you but hakuji helps him to walk towards you also douma is a simp to you also douma limps towards you lot,not bothered about his injuries.

Gyokko: "Guest..?"