My clients sister and I had been flirting for a year or so on and off. I was in my office on a weekend doing extra work and we were flirting, I told her to come and keep me company while I worked. She drove to my office and I let her in. We continued flirting and bantering, and she had moved to sitting on the side of my desk, her feet resting on my lap. I had my hand on her legs and was running them up and down her legs. She started rubbing one of her feet against my cock, feeling it harden. I pulled her onto my lap and we started making out, grinding against each other. My hands all over her ass. I lifted her onto my desk and pulled her tights off, going down on her. Her legs around my head and hands in my hair. She then pulled my head away and knelt before me, taking my cock out and sucking it and my balls. I then lifted her onto my cock and she rode me, then I stood up and put her on my desk, pounding her while holding her legs over my shoulders. As she was going through another orgasm, I pulled out, turned her around and bent her over my desk, pounding her pussy hard before cumming deep inside her. I pulled up her tights and watched a patch of my cum appear at her crotch. We continued flirting and bantering, and fucked again an hour later.