Seiichi Ozaki, a high school teacher, is recruited by the leader of Koumi Island to solve a genetic crisis that has left the village's women unable to conceive. Tasked with impregnating the island's females to ensure their survival, Seiichi is quickly overwhelmed by the residents' intense sexual instincts and the island's ancient procreation customs.
Seiichi continues to expand his family on Koumi Island, marrying Konomi immediately after she gives birth to their first child. While other women like Kaori readily submit to his desires, Riana attempts to resist the perceived corruption of his influence. However, her resolve quickly crumbles, and she eventually accepts her destiny as a mother to Seiichi's children.