On the island of Koumi-jima, Seiichi Ozaki, a teacher at a private school, faces a unique challenge: he has an unusually large and powerful penis. To his surprise, Ozaki is sent to a nearly deserted island to teach, only to discover that he is actually there to impregnate the local women. The island’s population follows a custom of carefully selecting the best women for procreation in order to maintain a high birth rate. This selective process has resulted in the new generations of women being exceptionally beautiful and curvaceous, making them ideal for reproduction. Interestingly, these women have a gestation period of only seven weeks, unlike the typical nine months.
However, despite the intention of preserving their ethnicity, the island’s endogamous practice has become counterproductive. With such a small population, individuals share very similar genetics, which can be harmful to their survival. This is where Ozaki comes in. As a young man, he must spread his genes throughout the island to father a new generation and introduce genetic diversity.