The Kishigami family is trying to conceive on her ovulation day but is not blessed with a child. Then his sister-in-law Riko comes to visit, having run away from home after fighting with her husband for the same reason... Her brother-in-law Yuta is Kokoro by her voluptuous G-cup body that his wife does not have and makes advances on her. However, as they are both frustrated by the fact that they can only have sex on their ovulation days, their desires explode all at once. From that day on, the two of them start secretly seeking each other and become addicted to the pleasure of creampies, ignoring the risk of pregnancy...