So it starts out pretty simple. A group of seven friends are all hanging out, having a couple beers. There's a lot of flirting going on, and since the couch is full, one girl sits on the lap of her boyfriend in the arm chair. The brunette, although she has a boyfriend, is flirting with her blonde friend, who she finds rather sexy and has always wanted to invite to have a threesome with her boyfriend.
Then, who knows how it happens. Someone starts kissing, and then another couple is kissing, and then a shirt comes off. Everyone is too busy to notice, but then some pants slip off. Within minutes, the couple in the chair are fucking doggy style, the girl on the couch straddles her boyfriend, and rides him, as she braces herself against the coffee table to get more leverage.
The brunette is on her knees, getting it from her boyfriend as the blonde watches, touching herself. The boyfriend is inserting a finger into his girlfriend's butt to give the blonde a better show.
Yeah, you could say sometimes orgies just happen.