You can use cannon or ur oc!
For your oc you need a backstory, breathing technique (can have two), name, picture/drawing, height, age, and etc. ( tell me if I’m missing somebody)
「hashiras」
Kagaya ubuyashiki(master dude):
Shinobu kocho: me 
Sakonji urokodaki(water breathing teacher):
Giyuu tomioka: @vampyrsz
Sanemi shinazugawa:
Gyomei himejima:
Rengoku kyojuro: @malessa_tvhead_666
Muichiro tokito:@ANG3LSTXRZ
Tengen uzui:
Mitsuri kanroji:
Obanai iguro:
「Kamaboko squad」
Tanjiro kamado: @Junio_Tails
Nezuko kamado: @YOUR-LOCALM0M
Inosuke hishabira: @malessa_tvhead_666
Zenitsu agatsuma:
Kanao tsuyuri
「demons」
Kokushibo: @The-Hall0w-secret
Doma:
Akaza:
Hantengu:
Gyokko:
Daki:
Gyutaro:
Kaigaku:
Muzan kibutsuji:
「Uzui’s three wives」
Makio:
Suma:
Hinatsuru: