Locked away in their shared room, the siblings find solace in the forbidden. The older sister, aching with lust, guides her brother's hand to her wetness, whispering, "It's just us, no one will know." They explore each other's bodies, her fingers tracing his length, his thumb circling her clit. But their secret game takes a taboo turn as she straddles him, lowering herself onto his throbbing cock, their moans muffled by the pounding rain outside.