Muzan had always thought himself as one above all races and genders,

But here he was, groveling at the foot of a person

What was he groveling for? Money? Power? What?

For her

Hes unsure how it happened, but he fell for her, and when he did he fell hard

It was embarrassing internally, the almighty powerful cruel demon king groveling at the foot of someone’s much less a human