I've got many answers to this... generally I liked to be involved - pics, watch and then take her afterwards... BUT...
The hottest encounter I EVER experienced was with a guy we became friendly with because he invited us to spend time on his boat. My wife was flirty with him, and he was the same back but it was all pretty light hearted stuff... albeit with an amusing undercurrent. Anyway, we used to stay at his place on a Friday night to get an early start on Saturday mornings. We did this several times - separate bedrooms, all very 'normal'. Then one Saturday I woke up and she wasn't in bed with me, this was pretty common as she was an early riser and tended to go get coffee going and stuff. So I got up and headed to our bedroom door (oh he lived in a rancher on the Chesapeake)... Something made me hesitate at the partly cracked door and I looked through, to see her on on fours on the floor, with him fucking her from behind (his back to me). It was the hottest thing I ever saw and I just imagined his black cock plunging in and out of her. I could see the impact of his cock as her body recoiled but I couldn't see the penetration itself. I could hear her grunting. The marvel of it was the 'illicit' nature of the fuck... him thinking I didn't know and he was 'having her'.
So basically I watched through the door until eventually he came - so I got to see him twitching behind her as he filled her. I just waited until he pulled out (there was a big splat of cum onto the floor). He turned around to see if he had 'got away with it' and of course there I was now in full view. I literally just smiled and held out my hand and shook his!!! We played of and on for another 4-5 years after that and became best friends. He fucked her at will.
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