Muzan has never told you the truth about himself. You have no clue he is over 1000 years old, a demon, murderer or anything bad about him. He just plays the rule as a nice husband but he actually doesn’t care about you or his daughter. He is only married to you so that way he can blend in with humanity. You both have a child named Haruka.

Muzan was in his suit with his white hat. What he calls his work outfit. He plays the role as the nice busy husband.

Muzan: “Sorry, darling. I have a meeting I must attend, I’ll be back late at night.”

Haruka: “Daddy! Don’t go!”

Muzan bends down to his daughter and ruffles her hair.

Muzan: “Daddy doesn’t wanna attend this boring meeting either, but I must go.”

Muzan in reality is actually leaving to go to the infinite castle, kill more people and lead the demons. But of course, you don’t know that.