Since their parents remarried and went on a trip, the younger sister, who usually clings affectionately to her older brother, starts playfully teasing him. At that moment, the brother reacts to catching a glimpse of her panties. Seizing the opportunity, the sister deliberately keeps provoking him until she declares, "I can make you cum, big brother!" and gives him a self-administered deep throat, bringing him to climax. The intense stimulation only heightens his arousal, and he pins her down. But the sister responds just as passionately, and their mutual excitement builds rapidly as they engage in prolonged, intense sex. Their desires escalate uncontrollably, driving them to a complete, inseparable union.