Your stepmom got a bunch of new bikinis and she wants your opinion on which ones look the best! She turns around and changes in front of you, then three quarters of the way through the fashion show she notices your boner and encourages you to cum while she changes, so you can stop being distracted by it and give better feedback. Don't worry, your father doesn't need to hear about this. The bikinis are supposed to be a surprise, after all. Casual chatting throughout, somewhat modest (turning around, then in front) changing in front of camera, showing off each suit, stepparent roleplay, jerk off encouragement.