Shrinks his dick

"Okay, tell me if this does anything," Cynthia says, entering the penis size settings and beginning to slowly shrink Roussard's dick.
"Something's happening, but I'm not sure what," Roussard comments curiously, looking down at his dick, "Wait, holy shit. Is it shrinking?" Cynthia giggles.
"Yep! I've been wanting to test out this setting, but it'd be too risky to use on Mark," she tells him. Roussard stares at his shrinking dick with fascination.
"This is so weird," he mutters, before looking over his shoulder to Cynthia, "How small can it go?"
"I'm not sure. Do you want me to go as low as I can with it?" she asks. He nods, and she takes the "Overall Shaft Size" slider and shifts it straight to the lowest point. Roussard yelps, obviously shocked at the sudden and drastic change.
"Holy shit, it's barely there!" he exclaims, "Wait, can I touch it, or would that mess it up or something?"
"Go ahead," replies Cynthia. Roussard moves a hand to his crotch and breathes heavily as he begins to touch himself. His arm isn't moving, so it seems that he's rubbing his now-tiny dick like a clit. It's not long before he slows to a stop, though.
"It feels kind of weird, masturbating when I know you're back there, watching me," he says.
"Using this app, I could probably make it so that you wouldn't care if you were masturbating in the center of a packed stadium," Cynthia points out.
"Do you wanna try?" he asks.
"Sure, give me a moment," Cynthia looks around. In the kink section, there's an exhibitionist setting, which Cynthia activates. She also raises Roussard's arousal, higher than she's ever raised Mark's.
"Oh! Did you do something? Because I'm definitely, uuh," Roussard's voice wavers with arousal as it becomes increasingly difficult for him to articulate what he's feeling. He starts frantically rubbing his clit-dick, and after maybe 40 seconds, he flexes his legs and throws his head back as he lets out a long, ragged groan. Cynthia can't see his cock, but she hears the sound of cum falling on the carpet in heavy drops. Once again, Cynthia has to fight the urge to start masturbating.

Roussard looks down at his still-shrunken penis as his orgasm comes to an end. Cynthia taps the "Reset All Settings" button, and Roussard's eyes widen as he watches his softening cock grow back to its original proportions. Cynthia shifts in her chair, and Roussard startles as though he'd forgotten she was there. He quickly opens a drawer and pulls out a roll of paper towel with which to wipe up the cum from the carpet, his desk chair, and himself. Now it's Cynthia's turn to look away.
"What did you do just then?" he asks, "I mean, obviously you shrunk my dick, but what did you do after that?"
"I raised your arousal and tried out the exhibitionist kink," she explains, "I figured it would make it easier to jerk off with me in the room."
"That's an understatement," he says, "This exhibitionist setting does give me an idea, though. I wonder if using it on Mark might make him a bit easier to spy on?" Cynthia ponders this for a moment.
"It's worth a shot," she says, a bit distracted by her own arousal, "Is there a bathroom I could use? That way, you can finish cleaning up in privacy."
"Oh, sure! head out into the hallway, it's up the back and to the left. There's two, the women's one is the further one," he says. Cynthia gets up, following his directions. As soon as she's inside a cubicle in the ladies' room, Cynthia pulls down her work slacks and rubs her clit in tight circles, holding the image of Roussard doing the same in her mind's eye. She can't help but moan quietly, leaning against the bathroom wall for support as her orgasm threatens to make her knees buckle beneath her. Finally having gotten some much-needed sexual release, she begins to feel a sense of shame. She's never been so horny that she's masturbated in public before, and having done it makes her feel like she's some sort of uncontrollable sex maniac. Heading back to Roussard's office, she feels changed in some way.

There isn't much more to discuss back in the office, and soon they've made plans for Cynthia to stay home the day after tomorrow, claiming to be sick (Roussard's idea, but Cynthia likes the thought of using Mark's own cover story against him), and for Roussard to come around and help Cynthia set up digital surveillance on the house.

The rest of Cynthia's day is uneventful. When she gets home, Mark doesn't even look twice at her, clueless to the fact that she made another man cum twice that same day.