Nearly 500 years have passed since the so-called apocalypse where souls dominated their control over the human vessels and grew into fierce monsters.

A small frail kid saved humanity from getting wiped out of the face of the earth through his strangely powerful and unique techniques and taught them to the humans that followed him.

He became a legend and humans developed special powers called cranks from his teachings. Humans couldn't procreate anymore.

A very few thousands of last generation humans that remained or stayed alive by becaming crankers now constitutes the only humanity left on the planet.

And they should continue to keep levelling up their cranks by slaying monsters and siphoning their souls to stay immortal and most of them tend to form teams to increase their odds. 

Everything was wrist-slittingly boring like that until one of those teams went ahead and mistakenly awakened the legend kid from his deep, and sound slumber. 

--------- One Chapter @Everyday --------------------

Unfortunately, I don't own the cover. I found it on Pinterest. And edited it a little.