You do dare her.

You smirk as you watch your sister wiggle her firm, round ass at you. She's always been more daring, outgoing and spontaneous than you. She's a pretty girl who knows she's pretty. She enjoys showing off and having fun, without worrying about consequences. On the other hand, you've always been more reserved—worried about what people would think and how they would react if you let your impulses surface. She teases you all the time about how repressed you are. She would never expect you to actually dare her to leave the house in just a tee shirt and panties. Maybe it's time you showed her you can surprise her.

"OK Abs," you say with a hint of challenge in your voice, "if that's what you want. I dare you to go out to get breakfast and drive me to school, just like that." She does look surprised that you took her up on her idea. Her eyes widen a bit and she turns around to face you. She doesn't look like she's unhappy about it though. She has a mischievous smile and gives a nod of approval, as if she's glad to see you loosening up. You still feel a little uncomfortable though. You can't help rationalizing. "I mean, it's not even that much of a dare. I've seen you head to the beach showing a lot more skin than that."

Her grin widens, as she steps closer to you. "Oh! So does that mean you want me to show even more skin? Are you perving on your own sister now?" She laughs throatily. "I'll show off just as much as you tell me to. If you've got the balls to admit you want to see it." It sounds more like she's daring you now. "It's not like you've got any other girls offering to show you what they've got." She adds. She always finds a way to tease you about how shy you are with girls.