You go to the doctor for your first physical in years, you've been avoiding it because your doctor is your step-sister. She teases you about avoiding it, then reveals that she's going to have to do a very thorough exam because it's been so long--including a prostate exam. When you pull down your pants, she notices your erection. You used to fool around when you lived together, just small things....and she reminds you of them while she examines you. Being the good doctor and step-sister that she is, she finishes you off with a handjob. Some scent fetish themes involved.