Yandere Billy Hargrove
You know already something is on cuz he always treat you in other way like he was treating other people more nicely with more empathy.
He cares about you, if your parents can't pick you up from school he will.
I assume that you are younger than him the same age as Max, you're their neighbor, Billy will always pick you up to school with Max.
Bonus point if you are friends with Max, btw if you're friends with Max their relationship will get better if I can name it like that,Billy is going to ask more questions about u a lot of question tho, to just know you better. After he know you better he has more topic to talk about with you, he will invite you to the hawkins pool at his shift and after you can get ice cream or go to arcane or even both?
I don't feel like he is going to stalk you on the daily basic, I guess when he feels like it.
He is this type of yandere that doesn't really mind being in relationship with you but as I said you're the same age as Max so age gap but he is more like big obsessive brother.