I've wanted to have sex with my wife's best friend, Susan for quite some time. She's tried to seduce me into an affair several times over the years, but I've always been able to pass it off as flirtatious banter between friends and laughed it off. But the past couple of months she has been more brazen and persistent, often flirting with me right in front of both my wife and her husband. I want to take her up on her flirtations, but I know the two of them are not in an open relationship, nor do they swing.

I have never cheated on my wife, well not while we've been married, and deployment sex doesn't count as long as it stays on deployment. I did have sex with a couple of other gals while we were dating that Laura, my wife, didn't know about at the time, but never after our wedding day. I've also had a few deployment wives, and several one night stands in various ports. But while home, I've never cheated on my wife. But my wife has also had relationships when I've been deployed. And Laura has never fucked around on me when I was back home. We swing and occasionally swap for the night with a few very close couples, but we don't fuck behind the other's back. And that's why Susan’s not so subtle invitation to have sex with her has been hard for me to refuse.

Susan's husband, Jack, is a pastor, and unless they have a secret life that we don't know about, they do not swing. Nor has Jack ever had even the thought of having sex with another woman, let alone letting another man fuck his wife. Jack won't even watch a movie if it has nudity in it. Even if Susan was up to swinging with me and my wife, we wouldn't have her since she'd be cheating on her husband. We don't swing with only one half of a married couple, unless the other spouse just wants to watch, or we've met with both of them and know the other spouse is okay with it. Of course, we can't always know if a guy or a gal we pick up at a bar is married and looking for some extra fun on the side, and if they lie, that's their problem, not ours. There is no way Jack would be okay with Susan fucking around, so any fun with her would be adultery.

I know what you're thinking, isn't having sex with anyone other than your spouse adultery? While strictly speaking that is the biblical definition of adultery, my wife and I have the view that having sex with someone outside of the marriage unbeknownst to one’s spouse is adultery. Adultery is a secret extramarital sexual encounter. If my wife is fucking another man while I'm watching or also fucking her, that's not adultery. That's two married people enjoying their marriage bed with another person. It's adultery if my wife is fucking him behind my back or if I'm fucking another woman behind my wife's back. I know Jack holds to the conservative fundamental definition of adultery, so wife swapping is definitely out of the question.

Anyway, Susan's gotten so blatantly obvious with her flirting with me that my wife has taken notice. Laura even asked me a few times if I wanted to fuck Susan, and I've admitted that I did. Laura told me that she'd be fine if I wanted to take Susan up on her offer, but I brought up our own restriction about having sex with a married person without their spouse’s knowledge. Laura just shrugs and reminds me that Jack would never give agree to let Susan have sex with another man. If I really wanted to have sex with Susan, it would have to be without Jack knowing about it. A truly adulterous affair. Laura was giving me permission to not only fuck her best friend, but to violate our own rule on committing adultery.

Thinking about having an affair with Susan turned me on. Laura saw the result that talking about fucking Susan had on me and told me to fuck her and call her Susan.

I didn’t have to be told twice, so I did. Not only did I imagine that I was fucking Susan, I treated my wife like she was a cheating cunt.

I fucked her pussy hard as she lay on her back on the floor. Her legs over my shoulders so I could sink deep into her pussy. She came several times before I pulled out. Sweat was forming between her breasts and I began to feel that familiar sensation in my balls before I cum. Laura groaned letting me know she was displeased with me, but I let her know that I'd soon be inside of her again.

With her legs still over my shoulders, I placed my cock at the entrance of her back door and pushed hard. My cock was covered with Laura's juices, and as I pushed my thick purple head passed her sphincter, Laura placed her hands on my thighs and tried to push me away with a loud groan of displeasure. I ignored her.

"Stop resisting, Susan," I said to my wife. "You’re a cheating whore of a wife, and you're going to be treated like one."

Laura continued to moan and try to push me away while I sank more of my cock into her tight ass. The only lubricant used were her own juices, which was not nearly enough for her tight bunghole. I continued to fuck my wife's ass until all of my hard shaft was balls deep inside of her. There were tears running down her reddened, glassy-eyed face. Then, with my cock stuck completely into her ass, I began to ram it even deeper.

"Oh, God, Matthew," Laura sobbed. More tears ran down her face now. "Gentle, Matthew, please," she begged.

"Cunt whores don't deserve to be treated gently, Susan," I sneered back to her.

I knew she was not enjoying this as much as I was, but she hadn't used our safety word yet. So even with the tears and sobbing, I was going to continue to fuck the hell out of her ass. She did want me to treat her like she was Susan, and Susan was a cheating whore.

After a few more deep penetrating thrusts, I pulled my cock nearly all the way out, keeping only my mushroom shaped head inside of her tight ass. I then proceeded to fuck her with long, slow thrusts. The redness in her face faded and her sobs faded away. Laura looked up into my eyes and smiled. I sped up my thrusts, faster and deeper. Laura's breathing got faster and faster, and a tear ran down her cheek again. I told her I was about to cum, and she told me to cum inside her. I had other plans though.

I wasn't fucking my wife; I was fucking Susan, a married, cheating whore of a wife. I pulled out, crawled up to Laura's face and shoved my cock down her throat and came. She gagged and choked on my cock and cum, as half of it dribbled out the side of her mouth. But she never took her lips off of my cock. When I was done, I pulled out and sat at her feet.

"Thanks for that," I told her. "Now come clean me off."

Without a word, and still licking the cum off her face, my wife went down on my cock and began to clean me up. When my shaft was clean, she moved to my balls, licking up all of our combined juices. She cleaned me up very well; there wasn't a single drop of either of our sex fluids on me when she was done. I was completely clean. Laura was still a mess down below, but she had managed to clean her face while cleaning me at the same time.

"Is that how you're going to fuck Susan when you get the chance?" she asked.

"Yes," I replied. "But it was fun treating you like a cheating whore," I continued with a smile. "I haven't treated you like that in a long time. I think…"

"I want to watch when you violate her ass," Laura interrupted me. "That priss needs a good ass fuck."