"An unexpected turn of events..." Rena, my girlfriend's younger sister, comes to visit us at our shared apartment. The next day, my girlfriend leaves for a three-day business trip, and Rena returns, clinging to me sweetly, saying, "I'm lonely, so please stay with me." It was an extremely hot day, and we were both drenched in sweat. But Rena harbored an abnormally strong sexual desire, pressing her body against mine and seducing me relentlessly. Unable to resist any longer, I finally gave in and committed an unforgivable act. Drawn into her intense lust, we began a forbidden relationship, desperately devouring each other from morning until night.