Hours earlier she called me to see if we can meet to have a chat and some coffee or tea. It was really weird that of nowhere she would request such a...thing. No wife or husband , just the two of us for a chat.I agreed and set a time, somewhere in the middle, between her house and mine. Nothing to hide. Her now husband was not in the picture 12 years ago, they tied the nut, we were at their wedding and multiple times we have spent dinners, coffees and drinks, more than I can remember.I got to. Of course I left out some stuff reading my SIL body language and reactions. However I did bring up dancing how fun it was MIL lol and saying she haven't dance in a very long so I replied i could tell she had great moves. She then looked right at me and said I did to while giving a naughty look like she remembered how she got me hard and was grinding on it. She then said we should of took some pics bc we all were dressed up looking good. My wife was in and out of it all day bc she was super. “Now it is your turn and I’ll help you if you want?”I remained on the perimeter, thankfully forgotten as Shy moved her hands to untie the thread that held the top of her dress over her chest. “Are you sure?” she asked Cee.“Of course and it feels wonderful and cool. Go for it.”Shy took another gulp of wine and reached up to begin untying the thread. Cee leant back and, consciously I believe, swept her hand across her breasts, drawing attention to them, as Shy revealed her own under her bra.“Turn. With the window still open she turned around and leaned over to hold on to the window sill so that her ass that I worshiped so much came back to meet me so that my cock rested between her ass cheeks which were barely covered by a freshly cut pair of jeans, the touch of her cool skin gave me a raging hard on, and at that point she started moving up and down making me even harder. With my cock still between her legs I leaned over and put one arm around her neck and stood her up making her back.