My demon slayer au (kokuzan or maybe all x muzan)

In this story kokushibo and muzan are swap. Kokushibo is the demon king and muzan is hi uppermoon.

Well muzan was not really an uppermoon instead more like a lover... and muzan is a bit weaker then other uppermoons.

And when kokushibo and muzan met yoriichi (like muzan and tamayo met yoriichi and yoriichi defeated muzan and tamayo break free from muzans cursed). Muzan break free from kokushibo's cursed and live with yoriichi.

Years past and muzan met tamayo the sick woman and turned her into a demon so she can live.
From that night tamayo was with muzan(like tamayo and yushiyo) and tamayo being protective of muzan and love muzan