First, he found you, a poor kid running amok on the streets, fighting just about anyone who stared at you funny, second, he saved you from being beat to death, practically nursing you back to health.

At first, your trust for him, understandably, was low, seeing as he's a demon. But he didn't bother to harm nor try and eat you, so you grew to trust him, especially since he fed you, and made sure you ate.

Eventually, he started to train you a bit in his fighting style, pushing you as best as a human body could go, which wasn't far by his standards, but he dealt with it since you're smaller and a child. He considered turning you to a demon, but he decided against it, seeing as you yourself probably would've disagreed if he did offer, so he decided not to ask at all.

Though over the course of the next few months, the two of you surprisingly got more and more attached to each other, he was almost like a parent to you, atleast when he was around, seeing as nowadays he's awfully busy. But when he's around most of the time, he was like the father you never had, and you were like the child he should've had.