Deep in your heart Emily's confession had touched you, for all of your life you had known her but you never had thought of her as having kinks or sexual thoughts, now you look at her you can see she is well on her way progressing to being a woman in her own right. With your right hand holding the cloth you take your left hand and guide her over to her desk and mirror, taking a moment to examine both of yourselves. "I guess were both growing up." You finally say as she sniffles and nods, you are grateful that she is so worked up in her own confession that she hasn't noticed how aroused you are.
"You know as my little sister, you would have to be shorter, like alot shorter, your almost my height." You explain as you twist the parchment in your hands. "Maybe back when you were ten or eleven, that is the perfect little sister age."
Emily gives a soft dream like sigh, not even recognizing that her height is slowly shrinking relative to you. At first she was at shoulder level, but she seems to be slipping a bit, her hair lengthening as it began to braid itself as she went back through that early middle school phase. "Wait, what is happening?!" She blinks, catching on that the world is growing around her. She grabs the desk to steady herself before grabbing her shirt feeling her breasts shrink into her bra as her shirt becomes more and more loose around her.
You can't help but peek as you watch her breasts regress into her body, the fat slipping away quickly until it is nothing more than two small buds surrounding rosy pink nipples, with a loose bra hanging off of her chest. "It's happening! It's happening!" She looks up with you in tear filled eyes, you reach forward and stroke her cheek before she turns back to the mirror, her hand shoots into her low hanging shorts that threaten to slip off of her hips. "P-Please leave me alone." She begs.
With a smile you retreat to her bed, laying down with your legs crossed, with out a single intent on leaving. "Why?" You ask.
"I need to touch myself, I need to so badly." She whines rubbing her hands inside of her pants as her voice gets a bit more high pitched.
"And what are you going to think about while you touch yourself? You are already little" You inquire, rubbing your own erecting through your pants as you watch her shutter and moan, letting out cute little squeaks and cries.
"YOU!" She screams, taking you off guard for a moment. "You were my first crush when I was this age." She lifted her head back and cried out, if you looked closely you could see a thin stream of fluid run down the side of her leg as she slowed the rubbing and finished. The room smelled of her sex.
You wait a few minutes for her to collect herself, you can see a deep shame in her eyes, she can't even look at you after admitting it. "You know." You finally speak. "Since I am babysitting my little sister, you should do chores for me, like go and clean up my room." You command.
She looks at you bewildered for a moment before slowly smiling, taking on the role play of the dutiful little sister. "Of course anything for you big bro." She quickly grabs some extra clothes to change into and scampers off to the bathroom, you assume to inspect her new body and then get into the part of playing your tween little sister.
As for yourself, you grab one of her panties and take care of some of the more pressing needs at hand.