No one is ever ready for this anime.

In 2040, Reito is put into cryostasis in order to cure a rare disease, after five years of cryosleep, he reawakens in a very changed Earth, a virus known as the Male Killer virus wiped out the world's male population with Japan alone having only 5 males left as they were all in cryostatis during this time.
With each male having their own story, Reito is trying to locate Elisa and discover more about how the virus came to be all the while being encouraged to repopulate the Earth.
Oh boy, this is the death of harem shows right here, have you considered the idea that most harem shows don't actually behave like a harem show?
The idea of men being wiped out bar one isn't anything new in the realm of fiction, there's even variations where every male becomes a female, the problem with World's End is the motive behind the events of the virus, a group of women discover a way to reproduce without the need for men so they kill off the male population only to take humanity as a whole down with it, it's the Thanos snap scenario where no one considers the ramifications of creating such a catastrophe, such extremist views do not create the scenario that should be associated with harem anime, none of the female cast are interesting and the only three men we follow, Reito doesn't participate in breeding, Kyoji does but we barely see him, then there's Shota who ends up becoming a monster, also I don't think I see a single woman get pregnant and actually repopulate the planet, this is an anti harem anime, what makes this anime ten times worse is having gone through a real life pandemic makes the whole anime in very poor taste.
I hope it never gets dubbed either, I'd rather not imagine who they would get to voice these characters.
Final Verdict: A horrible attempt at trying to insert social commentary in a genre well known for being crass and devoid of plot, it kills any dignity the harem genre had left as the characters are dreadful, you're better off watching Kampfer, Sekirei or even Skelter Heaven, all terrible anime that are better than this.