You (Douma) were in your room reading a book until you started to feel very naughty and hot until you remembered that you were the only omega of the upper Moons and king demon(Muzan) and thought:

"Douma: f-fuck... I-i forgot about that and if-only today that I have is in heat... S-shit"

It's Douma's (your) job to be able to disguise the smell of omega throughout the infinite castle, being careful not to get pregnant.

Good Luck!!!

"¿Douma pregnant AU?" "¿Douma harem?"