A t-shirt, to start

"Let's start you off nice and casual." Amy heard Bianca breathe a sigh of relief at this and smiled to herself. What an idiot, there was plenty of fun they could have with 'casual.'

"Of course, there's no way you would fit in one of my bras, so we'll just skip that. Ah, here we go. I guess I don't mind if you stretch out this shirt--it's pretty worn, and, if I'm being perfectly honest, a little small on me."

The t-shirt she pulled out was one she had kept mostly out of nostalgia. It was a yellow Adventure Time shirt, though the print was mostly faded.

More importantly, however, it was a shirt designed for a 12-year old. On Amy's flat-chested, extremely petite, 5' nothing frame, it looked cute, if a bit tight and a little short, coming just below her belly button. She sometimes wore it when she was feeling flirt. But never without a bra; she obviously didn't need support for her nothing breasts, but this shirt was so tight and the fabric so thin from years of washings, that her nipples would always show through.

On Bianca it was going to look ridiculous.

"Um, that will never fit me," Bianca said.

"Well you'd better try anyway, unless you want to go out in public as you are."

Bianca reluctantly took the shirt and tried to pull it over her head. Soon, her arms and head were stuck, and Amy laughed as she bounced and squirmed trying to get it on.

"Help me," Bianca said, and then, reluctantly, "please."

"Sure, hang on just a minute." Amy took out her phone, took a couple pictures of Bianca, nude and helpless with her arms and head trapped in the t-shirt. She inspected the pictures, they were good, but nevertheless, she decided to take some video as well. "What's your number?"

"Why? What are you doing? Are you on your phone? I thought you were going to help me!"

"Just collecting some evidence, first. Now tell me your number or I'll send you outside like this and that will just be the start of your problems."

Biannca told her her number, Amy saved her contact info sent her the pics and video. "Okay, now we both have some nice pictures of you to compliment all the ones you took of me over the years. No deleting them unless I say. I'll want you to be able to show me whenever I ask."

"Ugh, fine. Now will you help or not? I can't get it on OR off!"

"Wow, you're really helpless, aren't you?" Amy said with a smile, as she approached her old bully.

"Yes, I- AAAAAAH, ah ah ah!!!"

Amy had started tickling Bianca's sides and armpits, forcing her to scream and squirm. Her big breasts jiggled and bounced with every involuntary laugh. The sight of her bully's helplessness made Amy wet, but there would be plenty of time for that sort of fun later.

"Plu-please stop tickling me!" Bianca gasped.

"Will you be good? Do what I say without further argument?" Amy said, not relenting in the slightest.

"Y-yes! I pr-promi-i-ise!"

"Okay, then." Amy took her hands of Bianca, "no more tickling."

But just as Bianca started to catch her breathe, Amy licked a finger and rubbed the front of Bianca's exposed slit, from her taint to her clit. Bianca gasped and grunted in surprise.

"This doesn't tickle, does it," Amy said, as she moved her finger in small circles over her bullies clit.

"N-no," Bianca managed.

Amy slid her middle finger inside her bully, and bent her finger in a 'come-hither' gesture, rubbing her g-spot and smiling as a shudder of pleasure rocked through Bianca's body, arching her spine.

"I like you helpless," Amy said, "I think I'll make you helpless a lot in the next for years. But it looks like you'll enjoy it some over that time, too."

She pulled her finger out, "of course, I can't let you enjoy it too much. Now let's get back to getting you ready for this party."

Amy dug around in her school supplies and pulled out a pair of scissors. "Get on your knees so I can reach," she said and Bianca, evidently still speechless from her earlier treatment, complied.

Amy used the scissors to remove the sleeves from the t-shirt completely and open the seams a few inches down from the arm holes. Then, she similarly cut out and widened the color so that the shirt would fit over her head.

Finally, Bianca was able to pull the t-shirt on. Even with the alterations, the shirt was pulled so tight that the seams pulled a few more stitches open.

And, no matter how much she tugged on it, she couldn't quite get it to pull down over her breasts.

"You can't make me wear this," she said, "at this point it's not a shirt, it's a necklace."

"Nonsense, it just needs a few more alterations," Amy said.

She cut a long slit across the front, and two in the back. This created just enough give that she could pull it down and and use her hands to roughly cram Bianca's boobs up into it.

Of course, this had several consequences. There was a sizable portion of Bianca's breast hanging under the shirt as 'underboob', and the tension on the fabric pulled the slit in the front wide enough to form a boob window and show some top cleavage as well. Additionally, the fabric pressed taught against her nipples, showing every goosebump on her areola, and the whole thing looked like it was about to explode at the seams.

"I might as well not even wear a shirt," Bianca said, looking down in despair.

"Don't worry, you soon won't be. But take shallower breaths, if you have a wardrobe malfunction before we get to the party, we'll have to start over. Now, we'll need something to cover your fat ass..."