Ideas For books and AUs

AU Demon slayer

So I was thinking like an modern AU. where the reader sees the ghosts of everyone that died and we can communicate with them. But, the demons race survived the final battles with only the top three upper moons remaining. It sound stupid but it's a what if AU i might use. And the souls are trying to teach the reader how to survive the demons. But, the reader starts to sympathize and relate to the demons within habits and small things in background nothing to large just small events that are relatable. The demons only survived becuase of a sigular piece from each of their bodies. Muzan however still is alive but gave up on the spider lily and is not truest aware or caring of what happens