So the top is not his first? He used to sell himself?

He didn’t, I'm pretty sure. The top is just making the assumption that he did.

What confused me is the panel when he asked him about it and the uke thought about his crazy neighbor

I have two theories…actually three. Either the uke and the seme were two junkies beating each other off in the past and just don’t remember orrrr the neighbours was a predator and groomed the uke from a young age. Three….it was his dad all along and not a “neighbour “