"Is there anything else you'd like, Mark?" Eve asked, kneeling down to bring them both back to eye level.
"Did you have something in mind?"
She shook her head. "Oh, no! I would never suggest anything, especially after you were so kind as to make me so tall. No," she said, sliding her hands up his legs, following the shape from his ankles up to his thighs, not daring to go any higher. "This is about you. What do you want, Mark?"
Mark blushed. "There is something..." he muttered. Eve lit up.
"Really? Oh, please, change me into whatever you want!" she begged. "I don't care what it is, you don't have to fear judgement from me. I'm your sister, I want to make you happy."
"Okay, then." He turned back to the Chronivac and input something new. "This one's going to be different."
She nodded at him, and he pressed enter. Eve's breath caught in her chest.
A warm feeling had formed in her abdomen. It took up the place of her usual period cramps, though was far more pleasant, a strange sensation as she felt something shift around. Outside her walls, her clit began to pulse. All at once, she felt her ovaries slide out of her body, closing her vagina behind them. They soon formed into two fleshy balls encased in a low-hanging sack. Eve gasped as her hands came to fondle her new testicles. They swelled in her hands, quickly growing to the size of quail eggs.
Not to be outdone, her clit swelled too, taking on a more phallic appearance as it did so. Two inches, it pulsed, then four, then six. Eve let out a moan as her other hand grasped at its length, humping her new erection into her fist. A full seven inches of hard, uncut man meat.
But Mark wasn't satisfied there, oh no. He had unbuckled his pants and began masturbating to the sight of his sister's burgeoning cock. His own seven-incher was hard as steel as he watched the moaning mess Eve had become. Her cock strained against the confines of her hands, twitching, then burst out of them, forcing her grip apart as it gained another two inches. Mark felt his own dick shiver at the realisation she was now bigger than him in that department too.
Higher and higher Eve's spire climbed, from nine to twelve inches in mere seconds. Her head tipped back as her balls overflowed from her hands, now the size of baseballs. The foot-long cock spurted precum as it surged another few inches forward. One and a half feet, it grew, then all the way to two. Plump, apple-sized testicles swung halfway down her thighs. Eve squirmed as pleaure flooded through her, her hands furiously rubbing over the shaft, slick and throbbing. It wasn't long before she brought herself to climax, her cock firing rope after rope of thick, white semen across her chest. Moments later, Mark followed suit, giving her another coat of white paint.
Eve lapped all of it up eagerly. "It wasn't what I was expecting," she mumbled as she licked it from her fingers. "You've given me such a large package! It's bigger than your own..."
"That's the point, Eve," he smirked. She tilted her head. "I like girls that are bigger than me. Knowing you can dwarf my manhood? It's so fucking hot!"
Eve's eyes twinkled. "Oh, I'm so glad you think that!" she said, a gleaming smile breaking across her face. Then, her voice dropped to a more sultry tone, her fingers winding up her huge shaft in a mesmerising dance. "Is there anything else you'd like to do to me?" she asked.