Ryan Morris was a sophomore in high school. He had a sister named Michelle who was a senior. As siblings did, they often fought over petty matters. Ryan was a self professed cool dude, and considered Michelle to be a huge nerd. Michelle was a legitimate straight A student, and considered Ryan to be a lazy slacker. Occasionally they saw eye to eye, but most of the time they would squabble over their differences. Ryan thought his sister sucked huge ones, and one day called her a "dumb fucking nerd who wouldn't have any real friends". That was a stroke too far. Michelle shut herself up in her room to cry, and Ryan... well, he actually felt guilty.
After a while, Michelle let him into her room to apologize.
"Michee, I didn't mean it," Ryan explained, "I wasn't thinking when I said that."
"It's... it's fine, Ryan," Michelle said, "I know you don't actually hate me, but... was there some truth behind that?"
"I... I didn't mean the no friends part," Ryan admitted, "You are a nerd though."
"Yeah, I am...," she said, "Is that so bad a thing though?"
"I... well," Ryan stammered, "I mean... there are some..." he noticed absentmindedly that his sister was suddenly getting thinner, or more so her waist was shrinking to absolutely cartoonishly wasp-like size. Her hips and butt flared out as her breasts suddenly spilled into her lap.
"Oh my god!" Ryan exclaimed, "Michee! You're..."
"I... I'm turning into a...," Michelle whimpered, "A Dumbfuck!" She stood up so suddenly, her tits started wobbling like crazy! "Ryan! I don't wanna turn stupid! You gotta help me!"
"UUHH! UUHH! Okay!" Ryan yelped, "I'll help, but only because it's my fault that this is happening... I think. Uuuuhhhh... Okay! You are a hot nerd who likes to wear sexy nerd clothes and has a really high IQ."
Michelle watched as her brain accepted this information and her appearance morphed to comply with it. She wore a white and yellow checkered button up that exposed her wasp thin midriff, tied in a bow underneath her heaving mammaries. She wore short khaki shorts and thigh high socks with sexy tennis shoes (well, as sexy as tennis shoes could be). Her brown hair was made into pigtails and she was given glasses with a taped up bridge. Her cheeks were dusted with freckles and she was given buck teeth, rounding out the first stages of her transformation.
"Ryan, I think it'th working!" Michelle exclaimed, having developed a cute lisp, "I don't feel any thtupider, but I am getting hornier. Tho what'th nextht? I'll leave it up to you."
"Okay, uhh," Ryan pondered, "You really like anime and stuff like that, and you like to share your anime love with other people. You also hate wearing underwear because you think they get too much in the way of your massive anime titties and pussy."
"Thweet! Thweet!" Michelle clapped and bounced up and down, making her bra-less boobs wobble wildly, "Tell me I have the betht grades in school and I'm a huge prodigy thtudent like Light Yagami exthept not a murderer!"
"Okay, uhh," Ryan nodded, "You're a genius with, like, a 300 IQ, and you know and remember everything from math and science and history to anime and Japanese stuff and sexy times! You also have, like, a humiliation fetish, like Darkness from that one anime Konosuba! Yeah, and you have huge nipple piercings that go through your fat nipples and your shirt too and they have these cute kitty heads dangling off of them!" He watched with excitement as her transformation solidified, taking in everything he told her. A huge, drooling tongue flopped out of her mouth and drooped down her chest, dripping her saliva on the ground. She looked down at her boobs, looking at her nipple piercings and making them jangle around a bit. A huge, dopey grin spread across her face as she played with her boobs.
"Michelle?" Ryan asked his Dumbfucked sister, "Michelle, are you in there?"
"Michelle? That'th not my name, you dummy!" she giggled like a bimbo, "My preferred epithet ith Thmarty-Boobth (Smarty-Boobs)! That'th thpelled Sth-M-A-R-T-Y-hyphen-B-double O-B-Sth, and for your information the hyphen ith very important! Thank you for helping me, Ryan! I forgive you now... ethpethially thinth... that inthult... made me feel really humiliated... ooohhh man~!" Ryan watched as the crotch of her skimpy shorts turn wet with girl cum. "O-oh no! I jutht came in front of you! I... I'm thorry... oh... I'm tho embarrassed!" She started fondling herself as her face turned red from embarrassment.
"I'm, uh, glad you like it," Ryan said, flush in the face, "I'm... gonna go now..."
"Yeah yeah, okay," Smarty-Boobs replied as her brother backed out of the room, "You have a good night! I'm gonna call the TheeDeeThee (CDC) and watch thome Jojo'th Bizarre Adventure before bed. I love you, little brother!"
"I... I love you too, Smarty," Ryan nodded as he shut the door, "You have a good night."