The Kishigami family is trying hard to conceive on the day of ovulation, but is having trouble conceiving. Then, her sister-in-law Riko, who ran away from home after her husband and wife had a fight for the same reason, comes to visit... Her brother-in-law, Yuta, was captivated by her glamorous G-cup body with big breasts that his wife didn't have, and he couldn't help but approach her, but his desire exploded because they were both in agony because they could only have sex on days of ovulation. was. After that day, secretly