Jerking off while watching Millie

I got a really good view of Millie through the crack at the bottom of the window. She's about 15 feet away from me or so, and I can see her big breasts slowly rise and fall as she breathes. Wow those things are nice, I think to myself while stroking my cock.

I'm close enough to see a little drop of sweat forming on the breast that is closest to me, then seeing it slowly run down the side of her big tit. I wonder if she likes getting her tits fucked? Am sure she does, she must get tit-fucked all the time with those massive knockers.

For a few seconds I close my eyes and fantasise about Millie wrapping her lips around my cock and me squeezing on those big tits as she busily sucks away. I wonder how many cocks she has sucked in total? Maybe twenty or more at her age, I am sure she is really good at it.

I beat my cock harder thinking about Millie and her big tits, it turns me on that I am in here jerking myself off while watching her and she has no idea. Wow my dad is lucky that gets to fuck her whenever he wants to. If I was him I could just march out there and stick my cock in her.

I feel the pressure building up and that I am soon going to cum. Outside I see Millie moving her hands, readjusting her big breasts and I cum while watching this, unable to prevent a small groan from escaping my lips.

Then, to my horror, Millie sits up straight and looks around. I instinctively duck down even though I am sure she can't see me, and when I look out again she is no longer outside. As quickly as possibly I wipe myself clean and sit down on the toilet, then I hear a knock on the bathroom door and Millie's voice asking:

"Matt, what are you doing in there?"