Weeks have passed since his wife returned to her parents' home for childbirth, and Sota has grown accustomed to their life together. Now, he begins to feel the loneliness of living alone. One day, his wife's older sister, Yuu, suddenly shows up and says, "I thought you might be struggling... can I stay just for tonight?" Sota happily agrees. However, Yuu starts acting unusually affectionate, pressing herself against him. Flustered and overwhelmed, Sota tries to escape to the bathroom, but Yuu follows him inside and forcefully presses her large, voluptuous breasts against him. This intense, heart-pounding moment marks a dramatic shift in their relationship, sparking forbidden desires and leading to non-stop creampie-filled encounters throughout the night.