Ok so I've been reading a bunch of Genshin Impact Sagau so why not have a Demon Slayer Sagau (since I haven't seen this, this is my AU but if someone else has done this please tell me)
From what I've just been thinking of God reader is actually the god that gives the Demon Slayer katana's the power to actually kill a demon by making sure the sun shines the brightest on the ore used to make the swords.
They were also the one that gifted the crows to talk to give the Demon Slayers directions.
I also think that they were the one that gifted Yorichi making him literally gifted by a god, God reader also told the Ubuyashiki family of Muzan and that they need to destroy him to free their family of the curse and how to protect themselves against the demons
God reader is also the one to give the Ubuyashiki family the ability of foresight as well as give Kagaya a voice to sooth people's souls
With the Corps rules another one was added which was that every Hashira estate every Wisteria House and at the Ubuyashiki and the Sword Smith Village are all to have at least 1 or 2 statues of you at least that anyone can worship as well as give offerings to you
A Ubuyashiki family member once asked what your favourite colours were and after you answered they ran off but they visited you the next day because they made you a bracelet with those colours you thanked them, and surprising everyone the child managed to live until dying of old age, so it's rumoured that if you have one of God readers favourite colour on you somewhere your mission or life will end in good fortune
All Ubuyashiki members pray to you at a statue at least 30 minutes a day that is in the wisteria forest protected by demons, no one but the Ubuyashiki family members are allowed to visit this statue or know of it since they wanted to keep it in pristine condition since this was the location you first appeared to the Ubuyashiki family
when the Hashira go on dangerous missions they would often pray to one of your statues for you to watch over them and help them save as many people as they can and many family members of the Hashira would pray to you that they would return home safe
Imposter AU God Reader actually had demon qualities like claws, horns, sharp teeth, demon markings, etc. but people felt it was controversial if you looked like a demon so they didn't use them in any statues, paintings or anything that had you in it. Only the statue of you with your demon qualities is in the Ubuyashiki family wisteria forest and the family is the only one who know of your demon qualities and have items of you with them shown
Might add more if I get more ideas