Adult PC Game: Kurai-YA - Middle-aged Man's Human Reproduction Plan Trial. Ver.2022.04.12 Final (eng) Archive

A virus spread throughout the planet that began killing off men.
Middle-aged men who survived had bottomless sexual stamina, and because of their
100% impregnating sperm, the government passed a law that stated
"women must not refuse sex from a man, no matter the circumstance."

This is the story of his attempt to save humanity.