Mark had become an expert surreptitious masturbater, he could do
it at the drop of a hat and not bat an eye when he blew a big
load of cum in his shorts! It started when he was about eighteen
years old when he found that if he went into the closet in his
bedroom, he could watch his older sister by looking through a
crack in a common air vent. Being nineteen years old, Mark's
sister had a much more developed body than any of the girls in
his own class. Sarah wore a 34C cup bra {Mark knew because he
looked in her dresser drawer}, and her nipples were a deep shade
of pink with very long nubs on the tips. Her pussy, while not
real hairy, had large pronounced lips that were plainly visible
even from across the room. When Sarah would take a bath, Mark
would slip into his closet to watch her dry off and get dressed
or ready for bed, and some times after she dried off, she would
just sit totally naked in front of her mirror brushing her long
blond hair, and it was at those times that Mark would pull out
his pecker an