Sneak up on them

You've had enough of just watching so you sneak into the cabin, approaching the two lovers from behind.

"Mmmph?!" Anna freezes in the mid of a motion as you grab her and put your hand over her mouth. She doesn't try to struggle at all, as she sees the machete in your hand and feels the cold steel against her skin.

Martina meanwhile hasn't noticed a thing, except perhaps for the short pause and the slight change of rhytm as her friend start fucking her again. This time it's you steering the thrusts however, with your own cock pressed up to Anna's back and making her whimper into your palm while she follows the movements of your hips.

Once you're certain of the russian's obedience you slip your hand from her lips and down to her front, groping her tits on the way before reaching her pussy. She groans and then moans a little as you're rubbing at her clit.

The dildo slips almost all the way out of Martina while you got your hand in between their hips, so you alternate for a while between rubbing one of them and drilling the other.

But you still hunger for stuffing them full with your cock...