Approach the pissing girls

Now that you've had a chance to verify that this world actually does run on the rules you asked for, it's time to act rather than merely just observe. The two teenage girls at the bench a few yards away look like a good opportunity to get started. They're both busty enough to be free to use, and truth be told, watching them both piss themselves in public like that is giving you a sudden and intense hard-on.

You stand up cautiously, feeling a little self-conscious about the erection tenting out your jeans. Intellectually you know that you have no real reason to be embarrassed here; the man you saw earlier face-fucking that woman had his cock entirely exposed, at least for the brief intervals when he didn't have it buried down her throat, and nobody else seemed to care, further confirming that public sex is socially permitted in this reality. Still, merely knowing that in the abstract doesn't instantly erase your almost reflexive reactions towards modesty and nudity. It's not so easy to override a lifetime's worth of habits, developed while growing up in a society with very different norms than this one has. It's going to take practice—albeit some of the most pleasant sort of practice you can think of.

You walk over to the other bench where the two girls are standing in the puddle of their own mingled urine, which is starting to drain away through a small grate set into the ground just below the bench. Hayley seems to be finished peeing for now, while Jazmin is still going, although probably not for much longer, as her flow has slowed to a trickle. They glance at you briefly as you get closer, as though in passing, but after you hesitate there for a moment without doing or saying anything they look at you more intently. "Um, is something the matter?" Hayley asks archly.

"Can I, uh," you clear your throat, "have sex with you?"

Hayley blinks in surprise, and Jazmin lets out a single sharp laugh. For a moment you're terrified you've broken some unknown rule of this world by asking so baldly, but then Jazmin responds, "Wow, you are an old-fashioned one, aren't you? Of course you can have sex with us." She says it with the casual scorn that only a teenager can muster when stating the blindingly obvious. The trickle of piss dribbling from her pussy finally stops, and she gives her butt a little wiggle to shake off any lingering drops before she stands up. Now slightly closer to eye level, she looks at you bemusedly. "You don't need our permission, obviously, we're both big-breasted whores." She lifts the hem of her crop top pointedly, revealing full breasts with thick dark nipples.

Hayley chimes in, "I know, it's like, have you never met any other cumdumpsters before?" For her part, Hayley bounces up and down on her toes briefly, causing her own heavy boobs to jiggle under the thin fabric of her top. Both girls show off their tits with a casual, even habitual air, as though it's something they do on a regular basis. Which it probably is, here.

"Just... making sure," you manage to say, a little off-balance from the mood whiplash. Maybe you should've found a more discreet place for your first foray into free-use sex, to avoid this sort of potential for embarrassment. Still, your cock is as hard as it's ever been, and these two are clearly all too happy to help you out with it. Hearing them calmly refer to themselves with such degrading terms is just icing on the cake. You unzip your fly and— wait, no, the jeans you're wearing now have a button fly rather than a zipper. Strange, you hadn't thought you owned any of those. When you think about it, though, not having a zipper makes a certain sense in this world, especially if you're going to have your penis out on a regular basis. The last thing you need is to get anything sensitive caught between the teeth of a zipper while you're trying to have a good time.

In any case, you unbutton your fly and pull your cock out, stroking it while you look from one girl to the other. The two of them look back at you standing there holding your cock, not surprised or upset by it but clearly waiting for you to make the next move. Now it's just a matter of deciding what options to pick from the vast menu of perverted desires unfolding in your mind.