Sister's fault for making you hard
Your sister deserved everything that happened in bed that morning. It was her fault for making you hard... for making you want her so badly. Maybe she didn't notice her big breasts bouncing out of her top when you tried to wake her, how those plump nipples almost touched your face when she straddled you during the ensuing tickle fight. But when your sister laid down on top of you, refusing to get up, her soft body against yours... it was too much. You flipped over, pushing her down under you. There was no way you'd let your little sister up until she finished what she started - no matter how wrong it was, no matter how much she protested. She was at the mercy of you... and your hard cock. Desperate and helpless, your sister had no choice but to do exactly what you said, to do whatever you wanted to make you CUM.