The global epidemic has take lives of almost all people on earth. Only a few were able to develop immunity to virus. When the epidemic has passed, became clear, that women are much more immune, than men. Besides, immunity from the virus dramatically reduced women fertility. Having survived the epidemic, mankind faced a threat of extinction due to low birth rate.
Survivors build new societies, and everyone had to solve problem with birth rate. Many societies adopt a law of women enslavement and creation of "forced harems". Every man can take as many women as he can afford. For some people, this become a profitable business. Including you.