Shuumatsu No Harem or in English translation, World'd End Harem is that type of story that will really get the eyes of men due to its story based around one man who happens to be the only guy around with hundreds, if not more women surrounding him fulfilling the male fantasy. This is similar to other manga by the likes of Nagasarete Airantou and Infinite Stratos, which the three share a common element- a dense MC.
Because of a virus with no known cure, our MC had to go into cryostasis and wait five years until humanity could make a cure. When the MC wakes from cryo his virus has been cured but there is a problem. The MK (male killer) virus has left the world in a female-only society devoid of any males left alive. This is where he gets introduced to his exclusive female agent, Suou Mira.
Upon waking up, Suou informs the MC of the world's current dire situation and asks him to help repopulate with more than 1 woman. As I said, this manga has a dense MC and guess what, he declines to do so. This reason is due to him finding out his girlfriend from five years ago is still alive and if he should marry any woman, he'd want it to be her. It's understandable to stay loyal to his partner, but this MC becomes ignorant and wimpy when he doesn't see the big picture. Humanity is on the brink of extinction with only a handful of males left and this MC chooses to refuse every girl's advance on him and pay his full attention to finding his girlfriend. This MC can be easily despised and encourage the reader to drop the manga.
Each chapter fails to bring in the excitement, likable character development and anticipation that any manga must have to keep its readers eager to wait for the next chapter. With these elements absent from World End's Harem, the only thing that's getting the manga out there is with it's Ecchi tag.
This manga deserves a 6/10 because its only good traits is providing soft-core hentai and lots of fan-service. This manga does have the potential to become better in every aspect it's lacking, but it fails to deliver. I recommend you read it for the 'plot', not for the story plot.