After losing his parents, Koji is forced to live with his older brother and his wife. He grows increasingly dissatisfied with his brother Yukikazu and his wife Rieko's married life. Then, a chance encounter changes everything between them. Koji's sensitive body begins to stir Rieko's uncontrollable desires. Her slender, seductive figure and alluring lips deeply affect him, shaking his heart. Will the feelings developing between them remain a single, fleeting mistake—or will they evolve into something far deeper? The story unfolds as it searches for the answer.