I had been assured that nothing would be forced and everything would be consensual. It was a long afternoon. She called to confirm arrival and tell me...how much she loved me, her room was fantastic. She had to go as she had her initial session to plan the weekend. Time dragged, I must have checked the computer a hundred times. At last about 6pm an email pinged in. It was brief, identifying a good first session with interesting results and that things looked promising for an easy quick process.. The elevator stops and she tenses up again as the doors slide open. I know, from the kind of person that she is, this lack of control must be driving her crazy. The thought makes me smile slightly. I take her hand and her waist again and guide her out of the elevator onto the roof of my building, my penthouse just below us. “We’re outside again? Are we on a rooftop?” she asks, clutching my hand as I lead her further into the space.“Shhh. You’ll find out in just a second,” I murmur, chuckling. Maybe you can come the next time I go off somewhere and can't afford to hire any hookers." Not that kind of friend. I meant my period is coming." You can't fly, or be in warm weather when you're having a period?" I meant it changes why you'd want to invite me." I'm really not very squeamish. That's one thing, and besides, I put all my hooker costs on an expense account anyway, and the company never checks to see if I really fucked them or not. We'll be okay getting away with it this time, I. But I have always been a horny guy. I do watch a lot of porn, than a guy is supposed to. But now as the events were unfolding I started to plan up how to corner her and get down on her.Then came one fortunate day, I had taken an off of 3 days as there was an event going on and it wasn’t compulsory to attend it. My sister is a studious girl. She never misses school and spends most of her day in coachings. This was also an advantage for me. I never wear underwear at home, so my dick was in free.