Eva, startled by the knock on her door, rushed to cover her breasts and crotch. She placed one hand over her chest and the other between her legs to cover her penis and testicles, which to a passerby would look very out of place on her female body. Thank goodness she'd made them small enough to hide with one hand.
"Edwin, Edwin!" The door burst open rudely to reveal Dawn. She had a nice petite face, long and dyed sky blue hair that flowed all the way down to her rear, a nice set of perky C Cup breasts, a fairly thin waist, and a nice round ass. Eva had to admit that as annoying as she could be sometimes, she had a slight crush on Dawn. But surely she could have bothered to wait one second for a response?
"YAGG!!" Screamed the naked Eva, cowering in front of the mirror.
"WHAT THE!?? Who are you and WHAT are you doing in my brother's room???" Dawn shrieked at the unfamiliar young lady.
"Wait! I... I can explain!" Protested Eva, at this stage thoroughly embarrassed at the turn of events. "Do you recognize me? I'm your brother, Edwin. Or at least, I used to be."
Dawn stared at her blankly.
"You see that on my desk?? It's called a Chronivac. I used it to change into a girl." Eva continued. However, she wasn't ready just yet to admit to her sister that she'd turned herself into a dickgirl. Seeing her brother as a girl was probably enough of a shock for now.
Dawn squinted, and continued to stare. "Okaaaay....?"
"Look, could you just leave my room and pretend you never saw this?? Please?" Eva had never felt more uncomfortable in her life. She shifted her weight to the other foot, and then back again. Her balls were starting to feel squished, and her hidden penis was hot from embarrassment under her manicured hand.
Dawn didn't budge. Her eyes flickered as her expression began to change.
"Dawwwn... please please please go." Eva felt her small prick hardening. Somehow, from the weirdness of this situation, she knew this was going to happen.
Dawn cracked a smile. "Not so fast... you said this Chronivac can make changes? I wanna see!" She marched straight into Eva's room uninvited and pulled up a seat in front of the Chronivac. Eva was still huddled by the mirror, incapacitated by her desire to cover up her nudity.
"Pleeeease! Stop! You don't get it!" Eva pleaded. Dawn ignored her, her thoughts immersed in the Chronivac's thousands of options for customisable changes. One option in particular caught her eye.
"Oohhh... I'm gonna try something. Ready?" Dawn looked over at Eva and grinned wickedly.
"No!!" Eva begged hopelessly from across the room as her crazy sister behind the keyboard pressed enter.