This...reads weirdly like one of those mind-control stories. Brian wasn't really into guys, but then he met this guy, and for some reason, was just really into guys, but especially that guy. Not entirely, but there is a bit of that vibe going on.
Also, I guess I find dirty talk weird when it's not couched in some sort of a headgame thing or something? Or I dunno, that was a really terrible way of explaining it. Like...I dunno, if it's used in some sort of D/s sort of thing, then I just kind of fly by it...I dunno, maybe I just find dirty talk weird, period. But anyway, yeah, I found all of the "fuck my tight black ass with your young white cock" really weird. (maybe it's different because this brand of dirty talk is more elaboration upon the physical process of sex that's going on? I don't even really know.)
I think the main thing that makes it seem like a mind-control thing is I have absolutely no idea why Brian, who's "straight," is suddenly so desperate for cock. And for a straight guy, he sure had no compunctions about getting all freaky with dudes. Like wow, this guy don't got enough cishet white guy cred, man. Yeah, I dunno. Maybe it's elaborated upon more in the other installments. Or maybe it's just plain erotica and I shouldn't be searching for in-depth characterization and plot development here.