Mei, who has no children, ends up babysitting her husband's colleague's son, Hiroto. Despite her initial hesitation, she enjoys the novelty of having a child around with her husband. However, Hiroto, surprisingly knowledgeable about sex for his age, fixates on Mei's large breasts, eventually transforming her into a "sow semen tank" through repeated insemination training sex. Joined by two of Hiroto's friends, Mei is driven to the brink of insanity by the daily ritual, her primal instincts awakened, leaving her completely captivated by the young boys. What becomes of Mei? Note: The content may vary depending on the distribution method.