You had been turned into a demon, and it mildly annoyed you, muzan killed your family then expected you to work with him?!

HELL NO!

you often would protect demon slayers from demons

You encountered a boy, he had short ish hair with a red hue to it and maroon eyes and he had a demon next to him, you assumed it was his sister

They were struggling with the demon, and if sombody didn’t step in they would most definitely die