A world where semen is a precious resource

Humanity faced an unexpected crisis after the number of male births suddenly dropped drastically. Sooner than later, the ratio of man to women were of 1 man for 10000 women. The world's population decreased rapidly. Every government took matters into its hands. The country you were born in enacted a law that mandated every single man should always ejaculate intravaginally. On the other hand, women ought to take a fertility exam as soon as they are eighteen. Once they passed the test they were allowed to wear a neckband that indicated they were ready to be impregnated at any time. To reward the women who birthed males, the government subsidized them generously. A general sentiment of wanting to be impregnated was felt among the female public, who rarely even saw a man, as you could only find a 100 for every million women.

You are a high school student who attends an only female school and are expected to take on the role humanity needs.

(Based on the manga by Date Roku)