Riko Kishigami, who ran away from home after arguing with her husband over a secret affair, is now in her 682th year of marriage.

Riko Kishigami, the stepsister who has been trying to conceive but has been unable to get pregnant, runs to her younger brother's house because of a fight with her husband. When her brother, Yuta, sees her G-cup breasts, he can't help but stick close to her, releasing his long-suppressed sexual desires and enjoying the pleasure of ejaculation inside her, regardless of the risk of pregnancy...