Watched by Step-daughter

For years I've fantasized about my now step-daughter.  I've jerked many times to thinking of fucking her, though never ever really though anything could ever happen. Things took a big step forward this past weekend. Ever since I moved in a couple of years ago, I've been very careful about jerking off, only doing it while my wife was at work, and if the kids were home, I would make sure the bedroom door was locked and I would keep the sound off on the computer.  Since it was always mornings, I knew they would just think I was sleeping in and not really bother me anyways.  I of course had fantasies of Monica catching me and then fucking me, but knew that wasn't really going to happen and frankly didn't try give her the chance to "accidentally" catch me. A few months ago, Monica unfortunately decided to move out with her boyfriend.  My supply of sexy used panties was now gone, and I do miss at least looking at her sexy body on a daily basis.  She is 21 and has very thick long brown hair, quite nice sized tits, and a very nice shapely ass.  Honestly, over the last 3 or 4 years she has gained a bit of weight, but not so much that most guys don't likely picture themselves fucking her when they see her. Well, this past Saturday, a lot changed.  Her brother, who still lives at home, was out of town, which now meant I had the entire house to myself while my wife was at work.  I got myself set up on the bed with my laptop, some tissues and some lube.  Since I was alone, I could now just leave the bedroom door open and also have the sound on the laptop to enjoy the porn and cam sites I was watching even more. I had been stroking and edging for a good hour or so, and my cock was rock hard and slippery from the lube I was using.  I was watching a couple on a cam site really getting into it when I suddenly heard a noise.  I froze, first thinking I was imagining it, and then I could hear Monica call my name.  Still frozen, I was panicing, when I saw her in the bedroom doorway.  Apparently she was coming to do some laundry and my wife hadn't mentioned it to me.  She stood there with her mouth open, and I lay there stunned, my hand still on my now shrinking cock.  We both stammered "oh my god, I"m sorry" at the same time.  I started to move finally and that's when I noticed she wasn't exactly leaving.  She took a step forward and said to me "you don't have to stop".  A million things raced through my mind.  Was she going to fuck me? That was soon answered when she said "I want to watch you, I think it would be so hot.  We can't touch, but I'd love to see you cum". I couldn't believe my ears, and my cock was now getting hard in my hand again. I began to stroke it, and she watched intently, licking her lips and rubbing her crotch through her jeans.  I asked if she wanted to take them off, but she said no, at least not this time.  She just watched as I stroked and tried to keep from cumming too soon, but didn't last long before my red slippery cock erupted with hot cum.  It shot on my chest and belly and then more just oozed out over my hand and down my shaft.  I don't think jerking ever felt this good!  When done, she just said "that was hot" and walked away.  I cleaned up and when I talked to her about it after, she said she hoped we could do that again.  I don't know if she'll ever want to go further....or if I really want to for that matter.....but I'm definitely looking forward to jerking for her a lot in the future.  She did say maybe she'll masturbate for me some day, but not yet.  I can't wait!