You exit the bathroom, walking back into the bedroom with Kira dangling limply between your thighs. She feels heavier to you-- a bad sign, because you know it means she's starting to feel some arousal. You find Brooke lying face down, mostly exposed, with the sheets only covering her ankles and feet. You sit down on the bed beside your girlfriend's naked body and try to rouse her out of her sleep with a gentle shake of her shoulder. "Brooke? Honey? Wake up. We need to talk." She only groans into her pillow. You run your hand down her spine, over the small of her back, momentarily coming to rest on one of her smooth, round, soft buttocks. You hope it will coax her from her slumber more effectively than shaking her shoulder. "Come on, hon. Rise and shine. This is important."
Finally, she comes around, lifting up her face and opening her eyes. "Mmmh," she mumbles. "That was really spectacular, babe..."
"How much do you remember?" you ask, a little nervously.
"Hmm...," she sits up and thinks. "I remember I came really hard, lots of cum shooting through me... and I was... inside someplace tight, like a... wait... Was I actually inside somebody's pussy??"
"Yeah, you were," you admit sheepishly.
She looks at you with a serious expression. "... You... you fucked someone else?" The look of betrayal on her face nearly destroys you. Almost as an afterthought, she says, "Who was it? Everything is kind of hazy for me now. I don't remember anything except the sensations."
Somberly, you answer. "Brooke... please believe me, I'm so, SO sorry... I promise, I never meant for it to happen. Just... Kira came into the room while I was having fun with you, and... she jumped on me, and the urge was just too powerful for me to refuse her..."
"My SISTER?!" Brooke recoils with anger. "You fucked my sister?! While I was your penis?!? You mean THAT'S who I came into?"
"I feel awful about it, I really do," you say, trying to defend yourself. "I honestly couldn't help myself... I'll do anything to make it up to you, I swear... Please don't be upset at me..."
Brooke turns away, not saying anything for about a minute. You wait in tense silence for her response. At last, she softens and glances back at you with a humble smile. "I'm not upset at you."
Her words take you by surprise. "Wait... Really?"
She nods. "Really. It wasn't your fault, it was mine. I mean, I was your penis. I was so consumed with the thought of being inside a vagina that I didn't care whose it was, or that it meant you had to cheat on me. I know you. You would never be unfaithful to me. And you wouldn't have done this if I hadn't forced you into it." Brooke gives you a reassuring hug. "I love you."
"I love you too, Brooke," you say, sincerely.
"So where'd my sister go?" Brooke asks. "I AM still pretty pissed off at her, for taking advantage of you when you were vulnerable."
"Uh, well... Brooke? You mean you haven't noticed? Both of us have our full human bodies back."
Brooke looks down at her hands. "Oh! Hey, you're right! But, that shouldn't be possible, unless... uh, hold on. Are you saying that Kira...?"
"Yeah," you say. "Take a look for yourself." You get up from the bed and stand facing Brooke, with your pale new penis hanging there for her to see. Brooke takes one look and bursts into uproarious laughter. "What's funny about this?" you ask, your pride mildly hurt.
Brooke struggles to regain her composure. "I'm sorry. I'm not laughing at you, sweetie. It's just... this is the most brilliant instance of karmic retribution I've ever heard of. She pushed you into cheating on me, and then got herself actually turned into your dick. Don't tell me you don't see the irony in that."
"No funny," grumbles Kira's voice in your head. "Me be cock. No want be cock."
"Well, I do sort of see what you mean," you say back to Brooke. "It's just... it's really awkward for me, having your sister as my cock. I'm not sure what to do. Just now I had to pee pretty badly, and when I was done, I realized that she's starting to mentally devolve now like both of us did."
"Good," says Brooke bitterly. "It serves her right. You should keep her like that for now. I think being a mindless penis for a while is fitting punishment for her." A vindictive smile forms on her lips as a wicked idea crosses her mind. "In fact, now that both of us are fully human again... at the risk of giving her an enjoyable experience that she really doesn't deserve... what do you say you and I do a little experimenting, to see just how far over the edge we can push her?"
In your head, you can hear Kira make what sounds to you to be an anxious gulp.