He couldn't see her face and so couldn't judge her frame of mind. When he began washing her back, his erection simply surged. When the tip of his rising cock touched her ass, she jumped in surprise but laughed. Dustin said "Sorry sis... In a few seconds it's going to be out of your way..."

"What? You'll be able to make it go soft?" she whispered.

"No, no... It's just that it's going to be so high that it won't touch your ass anymore!" he replied.

When Lily began giggling at the thought, Dustin decided that she was teasing him and that she wanted what Emily had gotten. Which would...