Tired of their mundane life, a curious sister retreats to her room, locking the door behind her. She strips down, her heart pounding with anticipation. She slides her hand down her body, parting her legs, and begins to explore her wet, velvety folds. Her moans fill the room as she rubs her clit, feeling the pressure build. Unaware, her brother hears her through the thin walls, his curiosity piqued. He presses his ear against the door, his breath hitching as he listens to her pleasure, his own body responding.