He shows himself, in a very revealing way

You both look at where you heard the noise, and a bloke of around 50 steps from behind the tree. Lucy matches your gasp as you both see him with his trousers around his knees and his hand around his cock, a very hard cock.

“You dirty old man!” Lucy exclaims as she bursts into laughter. He makes no response, but instead stands there looking at you both, stroking his cock as if it were a perfectly normal thing to be doing.

“Well, aren’t you going to say anything?” you ask him, unable to draw your eyes off his cock. The sight is strangely erotic, the thought that this pervert is wanking at the sight of you and Lucy giving you a small tingle between your thighs.

“Sorry, just from when I first saw the pair of you walking along wiggling those amazing ass’s I couldn’t control myself.” His voice is one of a man deep in the enjoyment of his sexual act, totally unembarrassed by being caught.

“You hear that Dani, he likes our ass’s, think we should show him a little more?” she asks with a sly smile, obviously finding this whole situation as amusing as you do. Before you can muster an answer, she turns around, offering the man another view of her ass, outlined perfectly in her tight little skirt.

Not to be outdone, you turn as well, letting him see your ass next to Lucy’s, and leaning over slightly, you give a little wiggle, feeling your short skirt tighten over your cheeks.

“Oh god” you hear him moan from his hiding place amongst the trees.