You’d think after they defeated Muzan, it’d be over, right?

NOPE!!

Demons have been returning at an alarming rate, even though they’re supposed to be extinct. Thats because you’re in the picture, you’re the next demon king (or queen if you want), with invisibility powers and all others.

(Everyone survived and is alive for plot twist reasons, and they know you exist.) (This is from the Hashiras POV btw).