Your sister notices your bulge...

"Hey?" Your sister Lucy says, sitting down next to you. The bus begins to move.

"Uhhh... what's up, Lucy?" You ask, watching her breasts bounce. Her button up shirt is, well, not buttoned up all that much, and her full breasts and black bra are clearly visible. You cover your growing bulge, trying to look away from her tits.

"I can help you." She says, pushing her bright blond hair from her eyes. She begins to unbutton her shirt even more, eventually tossing it to the side.

"Lucy, you're..." You begin as she unzips your pants.

Lucy's bra is on the bus floor, her full and perky breasts out as she takes out your cock. "I'm your sister?" She finishes, smirking.

You grab one of her tits. "I'm gonna use you."