You're taking part in an experiment on some new fast acting laxatives, I come into the room, explain the new product, ask some personal questions regarding your toilet habits etc.. then I insert the new laxative and ask you to tell me exactly how you're feeling, what's happening etc. To be able to be thorough with the experiment you're not actually allowed to go to the toilet, you have to mess yourself in the room inside some pantyhose so I can see exactly what's happening. Once you begin getting some sensations in come over to see what's happening, you mess yourself in front of me, but I see it's turned you on.. which then leads to me encouraging you to cum too.