After you towel off and hide your new bottle of high-quality lube in your bedroom, you get down to work. This wishing stone is something you want to weild skillfully, and for that, you need to know what it can do. The obvious answer is tried first,
"I wish I knew the rules of this stone."
Nothing. Maybe that wish isn't allowed? Or maybe the stone's rules are so complex that it's easier to turn you into a sentient vagina than it is to teach you them? The rock looks so small. You wonder how big it would seem if you understood it entirely.
The next wish you want to make feels risky. Would you ruin the rock? Would you cause an explosion? But it would be so useful that you knew you should try. After a quick wish to make yourself and your room indestructible for a minute, you say:
"I wish that this stone could undo wishes."
Again, nothing. Zero for two, today isn't your day. Besides, of course, the part where you got to live out the most intense erotic fantasy ever experienced. This thought makes you smile, until you realize that you have no idea what your grandfather might have done with the rock. You're suddenly thankful that you brought it into the shower with you.
The next hour is spent making different kinds of small wishes. Now that you know everything is permanent, your earlier thoughts about ending poverty or world hunger seem too dangerous for now, while you still know so little. You wish for one of the coins on your desk to be unaffected by gravity, and it floats around in the air. You wish that 'it was pulled towards the earth with a force that was exactly like gravity', and the coin plops back down again as though you never changed it. After a while, you even try a few wishes involving other people, mostly conveniences for your family.
And after a few hours, you lean back in your chair, satisfied with your experiments. There's still a lot to know, but the stone appears to be able to grant pretty much any wish you'd find in a genie story, and it doesn't seem to want to harm you. Not that it seems to want to help you either, but all of your wishes go more or less how you imagine them going.
Mind wandering, you return to the memories of the five minutes you weren't human. Your pants start to tighten as you remember that for a brief period of time, you were a pussy, tucked away inside the pants of a woman on the bus while noone but you knew about it.
The rock sits on your desk, small and unassuming. You did good today, what would it hurt to treat yourself? You could make the same wish again. But this time, it could be longer than five minutes. It could be ten minutes.
Or, you think to yourself, your erection growing, even a few hours.
You pick up the stone, and say...
