RWBY Shrunk/Transformed

"Ah, to hell with it. I'll just have to deal with it. It's not like anything bad's going to happen." Yang adjusted her bra one more time before throwing on her signature yellow top, showing off her form well.
She picked up some shorts that were probably dirty, and then remembered that Ruby had a secret stash of cookies. "Well, just a few wouldn't hurt. I'm going down to the gym anyways."
She waltzed her way to the bedfort Ruby had set-up, throwing the shorts away for later.
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Ruby couldn't believe it. Yang was going to steal her cookies!? How could she? "Yang, if I ever get big again I'm kicking your butt!" Ruby yelled at Yang, knowing she wouldn't hear.
Unfortunately, Ruby's fiestiness would soon falter as Yang climbed onto her bed, nearly knocking down one of the sticks holding the bedfort up, and nearly crushing Ruby right then and there. Zwei cowered behind little red's legs as she looked up to the immense bottom of her sister, nearly bare save for a golden strip of fabric being swallowed by her cheeks.
"Uh oh..."
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"Where are those cookies?" Yang asked no one, "How does she always hide them so well?"
Crawling on all fours, her chest pressed into the mattress, dragging along as she scuttled forward, checking every pillow Ruby had in her bedfort.
"Does... This one have cookies? No. How about... This one, Ha ha! No." She checked pillow after pillow, until, finally...
"This one has a box in it! Jackpot!" She got up, sitting down on the bed, triumphantly holding up the pillow full of cookies.
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The bouncing of her chest was hell for Blake. It was like being shaken in a pepper shaker that was also a water balloon. (Not as fun as it sounds) Her head spun with each up and down Yang forced on her. The tight-fitting shirt didn't help, simply just pushing her deeper into the Yang.
The prison sentence - or rather the bouncing portion - got to its worst part as Yangs boobs felt like they were launching Blake to space and back. Yang's jumping onto the bed had caused her breasts to slingshot around, jumping with such force in each direction.
And then, if that wasn't enough, the flattening by the breasts, bra, and shirt was apparently not enough, as Blake's prison was slammed into a mattress, making Blake flatten across her breasts more that she thought possible. The dragging certainly didn't make it better for Blake.
She just wanted to leave here, go back to bed, and never leave there again.
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Ruby tried to run away as her sisters mountainous ass fell, but she didn't have time, and was forced up with the panties between her cheeks. Luckily, Zwei got away, and ran to Ruby's head pillow.
"At least he made it. Good luck, little buddy." Ruby gave a Zwei a nod, an appropriate alternative to saluting, seeings how her arms were being squeezed into her sides by Yangs soft, yet firm butt.

Ruby watched from her prison as the world shifted, Yang's butt moving with its owner as she climbed out of the bed and landed on the floor below.

The next sight horrified Ruby, as she watched below Yang's tight, black exercise shorts came into view. She tried to squirm out, but the girl was unable to escape her sisters cheeks. The pressure from each cheek was enormous and painful, as was the sight of the shorts slowly inching their way up Yang's slender legs.

Ruby knew she was done for, when...