Yuichi, who works at a major trading company, and his subordinate Aino are in an affair. The two are strongly attracted to each other and their relationship gradually deepens. However, Yuichi has a family and always returns home on the same day after their affair, so the two have never spent the night together... Their first trip to a hot spring... Their first night together. Away from everyday life, at a secluded inn with the scent of hot springs, the man and woman engage in a passionate and secret affair.