Billy would like it to be noted this is all Dustin's fault.
'This' being the current situation they're in, him and Steve sitting on one side of his table, Dustin on the other, attempting to explain to him how they're... whatever exactly they are. 'Boyfriends' sounds to cute for him (Steve rolls his eyes any time he says so) and he doesn't really know any other word.
Not the point, the point is apparently the kid's more observant than he bothered to consider, and he and Steve were "being to obvious" when he was bandaging the dumbass's hand. (He's not even sure how he got injured this time, he'd mumbled some explanation that didn't make sense, Billy's stopped asking).
(And they may or may not have been leaning into each other, more than could possibly be necessary, and Steve was staring at him with his "mushy look" (Dustin's term) but this is still Dustin's fucking fault).
"Is this why Steve moved in?"
Is this what meeting the parents feels like? If so he's glad he's avoided it up until now. (And he's going to very much not think about Hopper or Joyce finding out).
"No buddy that's not - this is pretty new."
Before Dustin has a chance to respond to that his door opens (they don't even knock anymore, he's let this get out of control) and Jane walks in, immediately looking confused when she sees them.
"Is something wrong?"
(As it turns out Jane's confusion mostly stemmed from how surprised Dustin was, and Billy couldn't stop laughing when he realized Steve thought the psychic girl had no idea).