She was my best friend's daughter.
I'd watched her grow up, her 'Uncle' in everything but blood, and she'd often been over my place with her family or when they needed to go out of town. Her and my wife never got along, although I didn't know why -- I always thought it was just friction between her and a young girl, especially since my wife never wanted kids, but even after she'd grown up the friction remained.
And damn, did she grow up. She had curves that a girl shouldn't have had at the age she had them, and as the years went by I couldn't help looking on occasion. It got more and more difficult to ignore her snuggling up to me on the couch during visits, or hopping into my lap... I was enough of a fool that I never realized she was doing it on purpose, always thought that it was innocent and I was the one having forbidden thoughts. But as I found out, she knew exactly what she was doing.
She knocked on the door one day when my wife was out of town visiting her sister, was all happy smiles and playfully asking if she could hang out for a bit, that she'd missed me. I couldn't say no. We ended up settling in on the couch to watch some innocent-enough movie, but she kept edging in closer, and closer... that sundress she was wearing giving me a view right down into her cleavage.
I tried to ignore as her hand slid along my thigh, figuring it was an innocent touch, even as it kept up, as it slid higher. She anticipated me starting to protest and looked up at me just as the first syllable crossed my lips, and the look in her eye forestalled me as she purred out, "I'm not wearing anything under this dress, you know."
I was shocked, and then she took my hand before I could react and slid it over her own thigh, pulling it up until my hand was against her bare pussy, until I could feel her eager juices spilling over my hand. I stammered something out, and then she leaned up, kissed me, and told me to shut the fuck up.
Things got a bit fuzzier from there.
Eventually my pants were off, her dress was just a circle of fabric around her midriff, and she was straddling me with a growl that she'd been waiting for this for too long. I could have resisted better, sure. I should have. I was married, for God's sake, and she was my buddy's daughter. But fuck, she was so hot, and she'd been teasing me for so many years that every taboo fantasy came rushing back-- as she pushed down onto me with a satisfied moan that sounded like an angel's harp to my ears.
She was worked up. I was worked up. It didn't take long of me watching those tits bounce, of grasping at her soft, tempting body with both strong hands, of bucking up against her and burying my cheating cock deep before I was close. I told her. I warned her. She moaned that she wanted me to cum inside her. I groaned back that I wasn't wearing a condom, that she might get pregnant. She all but whimpered as she ground down onto my cock and said, "That's what I want."
She got what she wanted. That time, and the next. And the next.