"Hmm...," says Brooke, looking at the rings and trying to decide. "Well... I can tell you're still a bit hesitant about this, honey, so to try it out, I guess I'll take the silver one, and you can have the gold one. I at least owe you that, for offering to buy them for me." Somehow it doesn't surprise you that Brooke would choose the silver ring; she always was the more adventurous one of the two of you. Still, you love that she's so considerate of you. As you hand her the silver ring and take the gold for yourself, though, she adds the caveat, "Just so long as we can switch at some point. I do eventually want to try out the gold one for myself."
"Uh, okay, I guess that's fair," you say. You watch as Brooke puts the silver ring on her finger, and then you slip the golden one onto yours. In a flash, Brooke vanishes, leaving her suddenly-empty clothing to fall to the floor in a heap. "Holy crap!" you exclaim. "These things ARE really magic...! Uh... Brooke?"
"I'm here," you hear Brooke say.
"Where?" you ask. "I can't see you."
"I can't see you either," she says. "But... I think I know where I am. Pull down your pants, sweetie. It's really stuffy in here..." You hesitate a bit, a bit flustered by the request, but you figure you'd better do what she asks. You unzip your jeans and let them fall to the floor, then cautiously, you slide your underwear down too and sit on the bench. At once, you hear Brooke sigh, "Ah, that feels much better. So, um... how do I look?"
What you see when you look down at yourself astounds you. First of all, your penis has grown about three inches. As you look closer, you notice that the skin tone of your entire groin area, including your penis and balls, is slightly lighter than the rest of you; in fact, it matches Brooke's skin tone perfectly. You can see also that your pubic hair has changed color too, from its normal dark coloration to Brooke's reddish-brown hue. And if there was any doubt remaining, it is quickly dispelled when you realize you now have a small heart tattoo on the side of your penis, toward the base of the shaft. You recognize that tattoo instantly as Brooke's, usually occupying a position on her left hip. It's unmistakable: Brooke has become your genitalia, just as the inscription on the rings had promised.
You fumble to answer Brooke's question. "You, uh... look like my penis. Only... maybe a little bigger..."
"Wow, it worked!" says Brooke. "This feels so weird... but in a good way. I can't really see anything, but I can hear everything you say very clearly... and my body feels so much more sensitive now. I can feel the slightest draft on my skin. It's like... I don't have all my senses anymore, but the ones I do still have are really heightened. Oh, you totally have to try this!" She pauses for a moment. "Hey, um... would you mind touching me? I want to see how it feels."
"Okay," you answer. You aren't sure why, but your uneasiness with the situation is subsiding rapidly. You reach down and stroke the shaft of your penis from tip to base with your finger. Instantly a shiver of pure pleasure pulses through you, and you realize why your mood has changed so suddenly. You can feel Brooke's emotional state-- her excitement, her satisfaction, her lust-- and it's having a very intoxicating effect on you. "Mmmm," says Brooke. "That feels... amazing..."
The possibilities flash through your mind. If a single stroke of your penis was that pleasurable for both of you... "Yeah, I have to admit, Brooke, you were right. This is so much more fun than I expected. We're definitely getting these." You rise to your feet and begin to pick up Brooke's clothing, setting the pile neatly on the bench. "Alright, I suppose we'd better go out and pay for the rings. You want me to turn you back now?"