Keep secretly watching.

You keep looking, trying to keep your eyes open just enough to see, but not enough to be suspicious. You see her pull off her top, watching the curves of her waist. She unhooks her bra, and tosses it to the side. You can see Mark unbuttoning his pants and kicking them off, sitting in his briefs. Emily undoes her pants, bending over to pull them down, along with her panties. Your cock hardens as you see her pert ass on display, not 3 feet away.

She stands up, stepping out of her pants. Her legs look amazing, but she's already getting to her knees. You watch her reach out, touching Mark's underwear. You feel yourself reaching for your cock. Are you about to get a glimpse of your roommate's penis? You watch intensely as she pulls his briefs away, a huge member popping up. It's only a shadow in the dark, but it's....massive.

"Oh my god...." Emily exclaims, forgetting for a moment to be quiet. In a whisper, she continues - "Mark, it's so big!"

"I know." You hear his voice, low but dominant.

Emily leans over. You can mostly make out a bob as she struggles to blow him. You rub your humble member to life, watching. She blows him for a while, her eager moans turning into whimpers. When she tries to stop for a breath, he keeps her there, holding a hand gently but firmly by her head.

"Do you want me to fuck you?" You finally hear. She nods gratefully. She pull her head off his cock, crawling onto his bed and posing doggy. You see Mark more clearly now as he stands up, his cock erect. It's huge, though you can't see it much in detail.