A Guilty Conscience

I've just returned from visiting my sister up North and as I sit here with a glass of wine I'm still trying to come to terms with what went on . Ruth, my sister, is married to a gorgeous guy called Andy. We've already fucked a couple of times whilst Ruth was out of the way but what happened on my last visit has stunned even me.

We were spending an afternoon in their garden, mowing the lawn weeding, planting etc, and as it was such a hot day I was dressed only in a tight top that just covered my boobs and a pair of cut off shorts that accentuated my curvy behind very well. Andy was striding about only wearing a pair of shorts and trying to get a bit of a tan as he trimmed hedges and shrubs.

Ruth had moved down the garden out of sight enabling me to steal glances at Andy's muscles as he toiled in the sunshine with his back to me. I was starting to get little tingles in my pussy as my thoughts turned to our previous sexual encounters and in order to take my mind of them I went inside for a drink. After gulping down a glass of cold water I went upstairs to the bathroom to clean up a bit.

I filled the sink with cool water and bent forward closing my eyes to splash my face and neck. As I reached out for a towel, eyes still closed, the water running down my cheeks, I felt a pair of hands grip my hips making me jump in surprise.

I spun round to find Andy grinning from ear to ear.

"Christ, I nearly had a heart attack I spluttered" - not at all amused.

"Sorry, I was just passing the door and seeing you bent over like that I couldn't resist giving your ass a squeeze," he replied.

"You want to be careful, Ruth might hear you and then where would you be"

"Unlikely, she's down the bottom of the garden hard at work in the vegetable patch - it'll keep her out of the way for a while " he said with a wicked grin.

Now it was one thing fucking my sister's husband when she was out at work or we were away for the day, but in her house, with her outside. I like a bit of danger but this was something else! However I had to admit I was tempted and Andy had to be able to see my nipples were hard as they protruded through the thin fabric of my top. What he couldn't see was the wet patch forming in my panties as a rush of desire overtook me.

I reached out to Andy, running my fingers across his chest and then moving lower to cup the very obvious bulge in the front of his shorts. Our eyes locked as I felt it twitch and throb trying to break free of it's tight denim prison.

"We haven't got long," I said.

"Better get to it then!" he replied.

As soon as Andy said this he spun me round bending me over so I had to grasp the edge of the sink for support. He leant over me , pushing my top up and roughly pinching and squeezing my nipples as my breasts swung free. Then he was unzipping my shorts and pushing them down with my panties until I could step out of them.

He must have removed his shorts at the same time because as he moved forward again I felt his cock butt between the cheeks of my ass sliding along the thin film of sweat on my skin.

Then he was moving it lower, the head searching out the entrance to my pussy, his fingers parting my outer lips and then driving it home. I grunted and took a firmer grip on the sink so I could push back harder, reveling in the feel of Andy's cock once more stretching my pussy walls and setting off the first ripples of pleasure that I knew would build to a shattering climax. I was not, however, ready for what happened next. After a couple of minutes of hard thrusting Andy pushed as deep as he could and wrapped his arms tightly around me, leaning forward to whisper in my ear.

"I want to fuck your ass," he hissed.

I froze - experienced as I was I'd never taken a cock up my ass and the thought slightly frightened me, however a delicious shiver ran down my spine as I thought about it for a second and then said quietly, "OK."

Andy slowly withdrew from me, my pussy walls trying to grip him, not wanting to let that beautiful shaft escape, but having no choice as he stepped back to reach into a cupboard and retrieve a tube of lubricant. He pushed me back down again and then squeezed a line of cool jelly down the crack of my ass before working it around my puckered hole, letting his finger slip inside, making me quiver with excitement and fear.Then he put a drop onto the tip of his cock and proceeded to rub it around his slick shaft. Moving behind me again I felt the rubbery tip glide across my cheeks and I looked back over my shoulders to glimpse his cock.

I swear I went weak at the knees as I saw the size of it. Moving down towards my vulnerable ass Andy's cock had attained new heights of hardness. The veins stood out in stark relief on his long shaft. The head had swollen to a beautiful purple mushroom oozing precum and shining with lubricant. I couldn't watch - he was going to split me in two! I felt the hot head press against my asshole and I tried to force myself to relax, but it wasn't easy. Andy applied a steady force and suddenly with an almost audible pop he was in. He paused, letting me adjust to his size whilst I panted trying to decide whether it was pain or pleasure that was engulfing my body.

"Ready?" he whispered, but before I could reply he pushed forward completely filling my ass with his hard cock.

It was wonderful and as I felt his pubic hair brush over my sensitive ass cheeks I realized that I hadn't been so excited in my life. Andy started to take steady thrusts , having to hold my hips tightly as the walls of my ass gripped his cock. Waves of pleasure were now washing over me as I reached down and started to finger my clitoris in time to his strokes.

That did it, my pussy started to spasm as I was helplessly wracked by orgasm. Andy could obviously feel the contractions in my cunt through the thin walls of my ass and with I loud grunt began to shoot his load into me. I could feel my pussy rippling and his cock pulsing as it seemed to shoot gallons of creamy cum into my virgin ass keeping me on a plateau of pleasure that threatened to make me blackout. With a final thrust of his hips Andy was spent and he pulled me up to a standing position with my back to his warm chest.

"From now on," he gasped , still trying to get his breath back, "I'll fuck you where I want , when I want - I'm calling the shots now!"

And do you know what? As I stood there feeling his prick slip out of me leaving a trail of sticky sperm to run down the crack in my ass I thought, "He's right, I'll do anything for his hard cock - anything at all!"

I started this relationship with my brother-in-law on my terms, but now I'm addicted to the excitement and danger and I can't see it ending! Should I end this affair and look for a man of my own or should I continue to betray my sister and write and tell you about my adventures?

Should I feel guilty?