A boy's innocent curiosity turns into a taboo temptation as he finds his sister's panties, still damp with her juices. His cock throbs with forbidden desire, and he can't help but whip it out, rubbing it against the soft fabric, pretending it's her pussy. His strokes grow faster, more urgent, his grip tight, until he's groaning, his cock pulsing as he paints her panties with his hot, sticky cum.