Fertiliverse

100 years ago, Japan’s birth rate sat at 0.2, the lowest in the world. The population was rapidly aging and the Japanese government was slow in making efforts to increase the birth rate. All seemed lost... That was until a perverted, but well-meaning scientist named Fujiwara Daigo proposed a solution. He had created a gas that had the following effects on women: 

• Increased breast growth in women during puberty.
• Increased fertility. About 3-8 children per pregnancy.
• Pregnancies are twice as fast.

• Increased hair growth. 

He argued that this would make women more desirable to men and it would encourage them to have sex and bare children. This is only partially true, as while he genuinely wanted to solve the birth rate and wanted others to have a loving family like him, he also had a perverted desire to have all women look like his wife, who had big boobs and long hair. The Japanese government found this solution to be unethical, but accepted Daigo's help as they were desperate and the gas had proven to be effective on test subjects. 

With their blessing, Daigo released the gas into the entirety of Japan. The gas was formless and odorless, so the public was unable to detect it. The effects of the gas would not become apparent until the current generation of girls went through puberty. The gas had no effect on women that had already gone through puberty. The gas reacts to changes in the body and amplifies and accelerates these changes. The effects of the gas are hereditary, ensuring they would passed down to future generations.

While Daigo was making physical changes to the population, the Japanese government under the leadership of the recently elected Kawajima Sadao pushed radical cultural changes. They combatted Japan's work culture by mandating employees are only allowed to work for a maximum of six hours a day, banning unpaid overtime and punishing workplaces that violate these new mandates. These new measures encouraged workers to have families as they now have time to spend with their families after work. These new measures were also effective in increasing employee productivity and happiness.

The government also made changes to the high school curriculum. High school would be dedicated to training students to become parents. The 1st year curriculum is mostly unchanged, but there are dating classes held to help students find a lover. 2nd year is when major changes occur. While boys are still being trained to enter the workplace, girls are trained to become mothers. Mandatory parenting classes are held to train girls to become mothers. They learn how to cook, clean, shop and care for children. Boys can participate in these classes too, but it is mostly girls who undertake these parenting classes. Girls can choose to study other subjects if they want, but they still are encouraged to become mothers.

In addition, the government changed how marriages worked. A couple would be considered married if the woman in the relationship was impregnated.

100 years after Daigo Fujiwara released his special gas into Japan, Japan's birth rate stands at 43.7. The Japanese government had taken a gamble on a crazy scientist's invention and it had paid off. People were having families again, very large families in fact. The voluptuous bodies of the women and the ravenous sexual appetite the nation's population had developed ensured people were frequently having sex and baring more and more children. Japan had developed a strong family-based culture. To them, children are the key to happiness.

High schools are not just places of learning, but where families are formed. Students often have children very early, usually in their 2nd year. Students usually spent the 1st year looking for a lover. The 2nd year sees mass pregnancies. In the 3rd year, 99% of the female students have dropped out to raise their children. According to the most recent surveys:

Drop-out Rate Survey