Ruby can't get Yang's top to stay on

Ruby placed Yang's bikini top over her tiny, perky boobs and reached behind her back to try to tie up. She tied it as tightly as she could.

"There! All fixed!" said Ruby, smiling proudly.

"Um, are you sure about that?" Yang pointed at Ruby's chest.

Ruby looked down and saw that the top was hanging below her boobs, completely exposing her nipples.

"Ahh! What am I going to do now?" said Ruby, using her hands to hold the top up.

"You could hand it to me and I'll put it on you, I bet I can do it tighter than you can!"

"Goddamnit, Yang, no! I'm not falling for that again!"

"It's not a prank this time, and besides, what choice do you have at this point?"

Ruby thought for a moment.

"Yeah I guess you're right," she said, handing the top to her sister, "can you put it on me please?"

"Of course! Turn around."

Ruby obliged. She couldn't wait for this nightmare situation to be over.

"What's taking so lo...?" she asked, but her question was interrupted by an unmistakeable ripping sound.

Ruby's worst fears were confirmed when she turned to face Yang and saw her holding half the top in one hand, and half in the other, before she threw them behind herself.

"Whyyyyyyyyy?" Ruby squealed angrily, "What am I meant to do now???"

Yang was beside herself with laughter. She knew she was being a bit cruel, but ultimately it was harmless fun.

"Oh come on Ruby, you'll laugh about this someday, it's hilarious!"

Ruby scowled and began to plot her ****. She noticed something that Yang hadn't.

"Hey, Yang, you know my top that you're wearing?"

"Yes..."

"It's way too small for you, you know?"

"Well duh, I can pull it off though!" Yang said, pushing out her chest and putting her hands on her hips.

That was exactly what Ruby was hoping for. She had noticed the top's elastic stretching and straining against the incredible pressure being creating by Yang's perfect boobs. Pushing her chest out was the last straw for the struggling top as it finally gave way. Yang heard the rip, but didn't dare look down.

"Please tell me I just imagined that noise."

"Nope." said Ruby, smiling as she held up the two tiny strip of red fabric that her top had been reduced to.