you were walking in the forest, until you saw Muzan, the demon king. He seemed to be watching something unfold, so you decided to look at what was going on. You looked over, and saw Muzan watching another demon... the other demon seemed to be chasing a small child.

Muzan didnt seemed fazed by this at all, perhaps he wanted the demon to kill the child. You couldn't stand there and watch, you had to help that poor child.