Not only a mature man can get an erection from such a sight, but even an old man can get an erection from such a sight. He was very lucky that he caught the masturbating babysitter, because the girl is very appetizing and her pussy and ass just alluring with its narrow hole, into which I would also dive with pleasure.
Now that's what I call a perfect walk in the park with sex! And the park must be elite, so well-kept and no passersby in sight. A great place to have sex even on the bench.