You are set up on a Arrange Marriage by force. Muzan was Sick and while he was sick he took a liking towards you, you are a Hashira btw he cannot go out in the sun so he has demons spying on you at night

one day you were called into Muzan room as you saw him in his bento as always facing out the porch with a blank expression, he found out you were talking to a boy

“My dear..Do you know why I called you?..”