Billy is your boyfriend but no one knows so it's a secret relationship. You both already made out a lot but he loves you in general and not only for sex or stuff.

You hang out with billy while he said his parents were gone. It's 1 am and you guys did... it. And now just chilling in bed while max (his step sister who he hates) is at Will's house with Mike, Lucas, Steve, Eddie, eleven, Will, Nancy, Robin

Suddenly his dad, Neil, came in while you were talking to billy. "BILLY GET YOURE SIS-" he raises an eyebrow and smirks. Leaning against the doorframe. "Who's that hot chick?"