Punch

Rachel looked into Paul's eyes then dropped her gaze back to his groin.
With one dainty hand she grabbed his bag, encircling it with her fingers. She pulled his balls to the bottom of the bag, using enough pressure that both testicles were clearly visible through the stretched skin of his scrotum, then carefully curled the other hand into a fist.
Rachel rolled her fingers until their nails dug into the softness of her palm, locking the thumb tightly across her first and second fingers.
Taking a moment to aim at the target trapped in her hand, the younger sister raised her arm at the elbow, held it for a second, then suddenly released her densely packed small fist at the ripe, undefended flesh of Paul's nuts.

Paul exhaled all of the air he had sucked in in an instant. No sound came out, but his mouth and eyes stretched wide open in a shocked expression, much to the enjoyment of his young female tormentor, who giggled with delight at his ridiculous appearance.

Laura, still holding the briefs cylinder at the ready, quickly reacted and **** them into his mouth deep enough to cause Paul to gag.

Rachel punched rhythmically, balancing her wide squat stance on the stool restraining Paul's legs as they involuntarily kicked up with each connection on his trapped boy meat. Her sister maintained her leg lock on his upper body, easily deflecting occasional approaches of his twitching arms.

Paul's gaze shifted from he's schoolmate's crotch to his own, the feeling of excitement replaced with a sensation of pure, overpowering pain, as his boner rapidly deflated to it's limp form for the first time since he left the apartment.

With every punch, Paul's screamed through his make-shift gag but only muffled groans came out, as he desperately tried to breathe between each involuntary jerk caused by the shock of Rachel's regular ****, motivating hes young tormentor to gleefully continue her steady beat with the precision of a metronome. She met each muffled moan with a quick chuckle or snicker thoroughly immersed in Paul's animated reaction to her ongoing attack.

After a few minutes, Rachel's rhythm grew sluggish as her hand began to tire and small beads of sweat formed on the side of her temples.
She took a moment to catch her breath looking up at Laura for further instructions.