After a few minutes, Brooke stops sucking your throbbing cock and pulls away. "Okay, hon," she says. "I've got another idea I want to try."
"What is it?" you ask, still catching your breath.
"Give me a sec," she answers, standing up. She leaves the room, and you watch as she walks into the bathroom. When she returns, she has a tube of something. She squirts a small dab of gel-like substance into her hand, and then surprises you by clutching your dick and rubbing it all over you.
"Wha... what are you doing?" you ask, alarmed by the suddenness of her actions. You can't deny, though, as she's tugging at your manhood, the feeling is strangely satisfying. Whatever she's applying to you has a bit of a cooling effect to it, and it's making your penis tingle. In your head you can hear Kira moaning with delight. "What... unghh... what is this stuff?"
Brooke smiles. "It's lube, sweetie. You know how you... always wanted to try anal? I... think I'm ready for it."
"R-really?" Your heart beats faster in your chest as you let out an audible gasp. Brooke has always been the more adventurous of the two of you, but sexually she has always had some pretty clear personal boundaries. Anal penetration is one thing for which she had NEVER seemed to show any interest before. Perhaps this whole experience with the magic rings is beginning to broaden her horizons. Then it occurs to you, briefly, that she may only interested now as a way to get some payback on her sister. Once Kira is back to her normal self, and back in her right mind, you can't imagine anything that would be more humiliating for her than the knowledge that she had been put inside her sister's asshole. But for the moment, you decide you don't care. The offer is too tempting, and your libido is too strong now to resist.
"Mmm," says Kira, oblivious to Brooke's request. "Feel nice... want be stroked... want fuck. Want pussy."
"Okay," you nod in agreement to Brooke. She helps you up, then bends down over the bed and spreads her buttocks with her hands, exposing her tight little asshole to you. "Alright, Brooke, I'm coming in," you say. "I'll try to be gentle." With your hand, you guide the tip of your erect cock up to Brooke's asshole. One small push later, and you're inside her, with the lube helping you slide right in.
"Mmmm!" shouts Kira gleefully. "Yes! Me fuck! Want more! Deeper!"
Instinctually, you cup your hands over Brooke's breasts, and feel her nipples against your palms. In turn she lets out a soft moan of approval. Both you and she are loving this. You push deeper and thrust harder.
Suddenly, a momentary bout of confusion hits you, and you unconsciously pause. You quickly recognize it as Kira's emotions affecting you-- a realization that is confirmed when you hear Kira ask, "... Pussy?"
"Why'd you stop, honey?" asks Brooke.
"It's Kira," you answer. "I think she just realized she's not in your vagina."
"Good," snickers Brooke. "Keep going. If you keep going, maybe she won't care. Hopefully this will teach her not to take things that don't belong to her."