Yuusuke was enjoying the rare freedom of living alone. That day, his wife had left for a one-night, two-day trip, allowing Yuusuke to relax at home. However, his older sister-in-law, Yuu, suddenly showed up, bringing unexpected changes to his life. Yuu harbored deep feelings for Yuusuke and had come to relieve his pent-up desires, though he remained unaware of her true intentions. Letting his guard down as she kindly helped with household chores, Yuusuke headed to the bath—only for Yuu to join him. From that moment, their relationship took a dramatic turn.