Dirty Promotion

My manager is really a good guy, but he's got a bit of a playful, cynical side to him, and we like exchanging playful witty banter. I've always thought he was a little attractive, but never let myself dwell on the thought since he was my manager and it was inappropriate, and also we are both in long-term committed relationships.
He's been complimenting me on my work a lot recently, telling me that I'm "kicking ass". In fact, his stellar reviews of me have landed me a promotion to manage another team in our company, so now he's no longer my manager but rather my peer. Now that this is no longer a barrier between us, I found myself craving his attention even more. Our conversations devolved from harmless jokes to flirtatious exchanges, the mutual attraction growing more obvious until one day we exchanged the following messages:
Him: Do you miss having me as your manager?
Me: Well, I do miss you bossing me around
Him: That can be arranged
Me: What did you have in mind?
Him: Come into my office

I make my way over to his desk, and he whispers in my ear "sit here and pretend like we're working". I prop myself up to his desk, angling so that my legs are slightly open in front of him and he can peek up my skirt. I am wearing see-through lacy underwear, which by now are wet and hot. He's talking work and giving me a serious lecture about code quality, as he pulls my underwear to the side and starts fingering me. Then he commands "turn around" and fucks me right there on his desk.