"Big brother, let's sleep together tonight," she says, her childish, affectionate words unchanged since childhood, leaving her older brother unable to suppress the turbulent emotions stirring within. On the hotel bed where they're staying, the siblings playfully cuddle with innocent ease. But the brother begins to notice—his little sister's body has matured into that of a woman, and he can't help but see her as a sexual being. Torn by these conflicting feelings, the brother hesitates, while the sister willingly accepts his desire. The moment they cross that line, a new, forbidden relationship is born.