My step-bro is a physical therapist, says he wants to help me improve my stride and help me learn to walk properly so that it’s more efficient and healthier for my feet. I get that, he’s a licensed physical therapist after all, but the part I’m kind of sketched out about is why do I have to be in my lingerie? He says it’s because he needs to see my “body dynamics in motion”, but I swear I can see a bulge in his pants. Is my step-bro using me to make his cock hard? I'm pretty sure he is but since I can't prove that I just continue to the consolation and walk on the treadmill as he watches my me from different angles to "study my movements".