Donna's Secret (MMF Bi Threesome)

Mike is excited because he’s slipped out of a party at work with Donna, the woman he’s been fantasizing about for months  now.  They head straight home to her place, and it looks like it’s going to be a fun evening for both of them.  Much to Mike’s surprise, though, her roommate comes home early – and it’s somebody that he never expected to see at Donna’s place.  Somebody else from work.  Suddenly the evening is heading in a direction he never even considered, and Mike needs to decide pretty quickly how far he’s willing to go…

Excerpt -
"She's been telling you about us?"
"Flirting? Playing footsie at the finance meetings? The way you keep looking at each other? Yup. She's been telling me."
"Sometimes I tell him about it when we're doing it."
Mike shook his head again.
"So you and I flirted and stuff all day, then you went home..."
"And told Paul all about it. While I made out with him. Yup."
"I feel like I should be offended somehow."
Donna stood up from the floor, walked over to Paul, and started unbuttoning his shirt.
"Well, that's your call. But I wasn't doing it to make fun of you."
She looked over at him while she peeled off Paul's shirt, then bent down, pushing her own pants off. The curve of her ass was a perfect half-circle in the light. When she stood up again she was fully nude.
"I was doing it because it turned me on. It turned both of us on."