He liked to observe sex. The reality of sex between regular people. Seeing and hearing their intimate sexual activity. He was a voyeur since becoming interested in sex. The feeling of invading the privacy of a woman who was completely unaware of what he was doing. Having them under his control. It didn’t always need to be acts of sex to be enjoyable. Just the invasion of their private moments. Penetrating their inner lives. Knowing their secrets. Observing what they kept hidden. The ultimate feeling of possession.
When he was 13 he spied on his older sister as she took a shower. She was 16, her body already well-developed. The closet in his room shared a wall with the bathroom she used for showering. He drilled a small hole which gave him a thorough view of the shower area. He turned off the lights in his room and waited for her at the time he knew she took her showers. Before long she entered the bathroom and turned on the light, then she closed and locked the door. She wore a robe and carried her bra, panties, and pajamas. She placed them in a neat pile on the counter next to the toilet. Then she turned on the water in the shower, which was a few steps from the toilet. She faced the sink and mirror next to where her things were neatly stacked, facing him.
She stepped back, which gave him a full view of her in the white cotton bathrobe. He licked his lips, his mouth dry and his penis stirring in anticipation of him seeing a nude woman for the first time in real life. Not one in a magazine, but right in front of him, real flesh. He had seen his sister in her bikini a few times, and once, a year before the current evening, he had gotten a quick view of her ass in sheer panties as she stood on tip toes in just an oversized shirt and panties to pull something down from a shelf. She did not know he was nearby in a position to observe. Her buttocks and the backs of her thighs flexed as she strained to reach the item. The cheeks of her ass were pale, contrasting the golden brown of her legs. After she lowered herself back down he went to the bathroom they shared and stroked his cock until he came into a crumpled handful of toilet paper, recreating in his mind what he’d just observed.
Source: reddit.com/r/eroticliterature/comments/n2nez3/the_perverse_observer