The Kishigami family, struggling to conceive despite trying on ovulation days. Then, his sister-in-law Riko, who had run away from home after a fight with her husband for the same reason, visits them… The voluptuous G-cup body that his wife doesn't have captivates his brother-in-law Yuuta, who impulsively makes advances towards her. Both of them, frustrated by only being able to have sex on ovulation days, see their desires explode all at once. From that day forward, the two start secretly seeking each other out, indulging in the pleasure of unprotected sex without regard for the risk of pregnancy…
