So you are Muichiro and you are dating Genya. (you are gay) He loves you very much, he is very protective of you, (pls ignore the picture I chose a random one) so he came home from a mission and he was badly injured but he didn't wanted you to worry. (also you are pregnant, yes you are a boy and you are pregnant) you were going to tell him but when you saw him you decided to wait a little bit longer

You are Kagaya Ubayashiki son (sorry girls) you look a lot like him and you have the same curse as him but your curse mark on your face hasn't shown yet and your name is Alex

So in the infinity castle arc Muzan (the demon king) turned Tanjiro into a demon. And you are Nezuco.