She had never seen anyone fucking, never even seen a photo of the act, but she had no doubt what was happening below her. The boy was behind the girl. He held her by the ass, and he was ramming himself at her. Every time he thrust, her body jerked forward, and he had to catch her by the ass and shove hard. Amy couldn't see the point of penetration, but her own body shivered and tensed with every frantic movement of the couple below her on the ledge, and she vibrated in resonance with their fucking.

Quietly, terrified now that she might make a noise and betray her presence, Amy eased to her knees. She held onto the tree for support and she peeked downward, her face flushed with excitement and wonder.

"Oh, God. Joey, take it out, take it the fuck out!" the girl squealed, and Amy knew what she had at least half-suspected from the first. The girl was her cousin, Betsy.

She fucks! Amy thought. Betsy actually fucks!

The boy eased back, his cock sticking out from his crotch. He was young, about the same age as Amy and Betsy, with a smooth, slim body. The only hair below his ears was the patch of dark fur that grew around the base of his cock. He was sorta cute, Amy thought, but she was far too excited, seeing her first erect prick, to pay much attention to anything else.

Betsy sprawled on her tummy, reaching back to rub her fingers through the crack of her ass. "Oh, God, I didn't think it would hurt that much!" she said. "It felt like you'd shoved a burning stake up my asshole!"

Amy gasped. She was truly shocked at what she was hearing. She had heard that people sometimes did fuck each other in the ass, but she had never really believed it.

"I liked it," the boy said. "It was wild, Bets – even tighter than your pussy, and it just seemed to suck on me, like a mouth without any teeth! I wanted to ram it all the way up you. Jesus, I still do!"