"You're a student on a female anatomy course, and your first assignment is a personal demonstration of anatomy and sexuality. You start off wearing something casual - jeans/shorts/shirt etc before stripping down. You talk about your body, explaining the different erotic areas - explaining using the scientific terms, and relating them to your own body. Except that you had to wait a little too long for our meeting, and regret having that coffee... You're obviously a bit restless as you demonstrate your breasts. Maybe you explain as you strip down more that your bladder is aching (maybe mentioning the added pleasure from the fullness, or showing your hard stomach). As you show more detailed and close up demonstrations of the genitals, you realise you're not going to be able to hold it much longer. You make sure to point out your aching urethra. Maybe you let a few dribbles out accidentally. Eventually you have to give in, and let it go, you try and make it seem like it's intentional - like you know there's an inherent link between peeing and pleasure."