A vivacious and alluring island girl who is one of the first women Seiichi meets and impregnates. Riana Tachibana: Konomi's sister.
The island's inhabitants have evolved a peculiar constitution where women reach full-term pregnancy and give birth just one week after conception. Seiichi's mission is to act as the island’s "head inseminator," impregnating the women to ensure the population's survival. Key Characters
The story follows , a high school teacher who has a penchant for visiting remote islands. Despite his mundane profession, Seiichi harbors a physical trait—significant sexual stamina—that he feels is underutilized in his everyday life.