"Please." Emily mewled softly, her eyes begging you to join her, "I... I want it so bad..." she said, rubbing herself more frantically as you watched her with an amused expression. This behavior was miles away from how she usually acted, and knowing that your words had brought about this change made this whole situation even more satisfying for you.
You walked closer to her, taking in the scent of arousal emanating from her body, "Mmm... You smell so good Emily." you said as you leaned down to kiss her neckline softly, eliciting an intense moan from her. "But I think that if you want me to join you, you'll have to show me how much you really want it first..."
Emily looked up at you with pleading eyes. "What do you want me to do?" she asked desperately, rubbing herself more vigorously now as her body screamed for release.
"I don't know... Maybe you could start by begging some more?" you said smugly, knowing full well how much that would torment her. She looked at the floor, redder than ever before looking up at you again with a pleading expression on her face. "Please... please take me..."
You couldn't believe your ears. The words came out of her mouth so naturally, well practiced, as though she had done this countless times before. She continued with increased desperation, crazed eyes darting the room. "I know I shouldn't want it... but what you said was true. I've always been aroused by everything, and... and that has always included my own brother..." she looked at the floor shamefully, unable to look you in the eyes anymore.
"Please! Please just take me!" She repeated, desperation evident in her voice as her body betrayed her even further with a moan of pleasure. "I'm so wet for you... so horny..." she pleaded, falling to her knees and groping for your member through your boxers and squeezing it gently to show you how serious she was about this whole thing. You couldn't believe that your formerly prude brat of a sister now knelt in front of you, begging to be taken by her own brother.