23(Demon Slayer)

An Au where the Hashiras(-Muichiro for obvious reasons) aren't only the strongest demon slayers but also Kagaya's spouses(I love Amane but here she will not be Kagaya's wife...still close to him and the hashiras but not his wife.).

How did this came to happen? Kagaya's parents knew their son wouldn't live forever and wanted to arrange a marriage for him and at first they approached Amane's parents but unfortunately Amane had already accepted to marry another person(maybe it could me Mui and Yui's father so the twins will survive as will their parents...but it is up to the writer who it is or if Amane actually marries someone) but offered their service as a family were the woman are matchmakers to find the perfect match for Kagaya which the couple accepted.

Amane met Kagaya and asked him a few things before deciding that besides finding the best match(es) for him that she would also be his friends as he seemed lonely.

She started a journey through different villages to meet all available young men and women while sending letters back and forth with Kagaya.

In one of the villages Amane met the most cheerful and sweet boy and his big sister and she knew the boy, that later she learn was named Tomioka Giyuu, would be a good match to her friend but as he was still young she talked with Tsukato(as they had lost their parents) and offered them to reside with her family until Giyuu was old enough to decide if he wished to marry Kagaya and that would give them time to get to know each other. Tsukato wasn't sure about this but as she knew that if something happened to her, Giyuu would have no one else she ended up accepting Amane's offer and later Tsukato ended up meeting her own fiance who was Amane's cousin(and Tsukato probably wouldn't die on this au...or she may since it is up to the writer).

Kagaya ended up agreeing with Amane's choice as he found Giyuu to be an amazing boy full of life and even after learning about the story of the Ubuyashiki family and about demons, Giyuu simply said he would learn to fight demons so he could help Kagaya in ending the curse on his generation(and this lead to Urokodaki taking Giyuu in as a student but if Sabito and Makomo die/are dead is up to the writer).

Amane kept traveling despite already finding a good future spouse for Kagaya and surprisingly in the following villages she visited, she met other people that she found would be an amazing match to her friend which left her unsure on what to do so she simply wrote a letter to Kagaya and Giyuu(who despite not having yet agreed to marry Kagaya, or more he did but everyone said for him to wait a few years before actually agreeing as he was still young) about it.

Kagaya while knowing that some leaders before him and his father had more then one wife, he didn't believe he could do the same to his future spouse but Giyuu disagreed with him on this as he believed that Kagaya deserved many people to love him and even if Kagaya didn't end up marrying them they could offer the same thing they did Giyuu as from what Amane said, some of the people she found needed a way out of a bad situation(also Obanai's story would be a bit different, in the case that Amane was the one to realize that something was wrong in village she passed by and informed the demon slayers so Shinjuro saved Obanai a bit earlier and he and Ruka adopted him).

So Kagaya ended up agreeing to what Giyuu said(mostly because Kagaya learnt that he had a hard time saying know to Giyuu when he looked at his eyes which he and the rest of his spouses will forever be teased with even after he has gone blind) and soon found himself meeting more 8(Gyomei, Sanemi, Mitsuri, Obanai, Rengoku, Shinobu, Kanae and Uzui) more people all between the age of Giyuu and Kagaya's with only one of them being older then Kagaya.

Slowly the group got to know each other(some had a easier time like Kyoujuro, Mitsuri, Kanae and Giyuu but others had a harder time like Obanai, Sanemi, Shinobu and Uzui with Gyomei being more in the neutral ground with Kagaya) and grew close with each of them helping the others with their trauma(also Sanemi's whole family and Gyomei's orphans are aloive...except for Sanemi's father and Kaigaku never met Gyomei and the orphans a she ende dup in Jigoro's care) and also training as all of them decided to become demon slayers to help Kagaya especially as most of them weren't completely sure if they would accept to marry Kagaya or not and this was a way to thank him for helping them.

When Kagaya turned 20, he married his first spouse(Giyuu) and seeing how Kagaya still cared about them as much as he did Giyuu made the others also decide to pursue marriage with Kagaya and later marry him too.

By the time Kagaya was 23, he had 9 wonderful spouses, 13 children(5 by blood, 8 by adoption and said 8 are Gyomei's orphans) and despite being blind he was proud of how far the slayers of his generation(especially his spouses who had all became hashiras so Muichiro will not really be an hashira here but he will be the strongest non hashira slayer until Tanjiro comes).

How would this affect canon? Mostly it is up to the writer but the hashiras will also be in a relationship(except Shinobu and Kanae for obvious reasons) so they will be much closer then in canon, while reticent about Nezuko they would take their time to see what made Giyuu decided to spare her(because their spouse may be many things but he isn't one to make rash and stupid decisions without a good reason behind it), the kamaboko squad would end up unofficially adopted(technically Kanao is already Kanae and Shinobu's adoptive sister and Genya is Sanemi's brother) by the Ubuyashiki polycule and everyone would survive the final battle and the ones before(so no Kagaya deciding to go 'Boom!' or Kyojuro ending up a donut) even if it is with a few less limbs(these are the ones in my mind for now).

Also, if the author makes this a ABO, Mpreg or trans man then the Ubuyashiki siblings wouldn't be quintuplets(at least in coming from the same birth giver...they may be born in the same day but with different birth givers) and Hinaki and Nichika's birth giver would be Kanae, Kiriya's would be Giyuu, Kuina would be Sanemi's and Kanata's would be Mitsuri(of course that the writer may choose different people to be the birth givers or keep the Ubuyashiki children as quintuplets).