Shuumatsu no Harem or in English translation, World's End Harem is similar to another manga/anime by the name of Nagasarete Airantou where there is only one male surrounded by a large female populace who will do anything to get "busy" with him to repopulate, but the MC refuses because of some stupid reason and becomes the "wimp MC."
Our MC has just woken up from 5 years of cryostasis to find out that the MK (Man Killer) virus has eradicated the male populace, leaving the world in a female-only society. The MC is asked right off the bat after finding what happened to help repopulate. In any man's situation, the answer will be a straight yes. Unfortunately this MC rejects the idea to do so and shoots down every advance any female makes on him.
This reason is because his girlfriend from 5 years ago is still alive and he wants to do anything to find her to marry her. It's understandable to stay loyal to his partner, but this MC becomes the dense and stupid harem guy when he doesn't look at the bigger picture. A world crisis is happening with humanity on the brink of extinction with only a handful of males left and this MC's first choice is to find his lost girlfriend ignoring this world crisis. This MC can easily be hated and can encourage the reader to drop this manga.
The story is getting more uninteresting per chapter with little character development going on. This manga doesn't have conflicts or scenes where it makes the reader wait in anticipation for the next chapter.
In conclusion, this manga is purely for fan service and soft-core hentai. 6/10.