Adam explains

It was clear to Adam that he would fuck Sarah. She was his sister - but it did not matter. His sexual morals were gone.

He wanted to finally lose his virginity. To his crush Heather, the school slut. Or to his sister. It did not matter. Sarah was a gorgeous girl, cheer-leading captain. Every boy in high-school would jump at the chance to have a shot with her.

That did not matter to Adam. He wanted to fuck. Sarah was gorgeous. She had a pussy. That was enough.

Adam was slowly moving closer to Sarah.

"Adam? What are you doing?"