Sins Paradise: Domination System - Chapter 27: Five Nuns

In this world, orphans or just anyone without any hope for this world can apply to become a “walking target”. Their sole purpose is to be a practicing dummy for the students of the sect who train to become “Demon Hunters”. These students need “walking targets” to test their training on living, walking beings of flesh and blood.
In exchange, they will be provided with food & shelter.
Their existence value is lower than a slave, but if they manage to survive a few years they can receive a life long pension.

Xiao Han is such a “walking target”. One time he witnessed a powerful Demon Hunter disposing a demon. When the demon died, a fragment of the demon that managed to escape entered Xiao Han’s heart. No one saw that, and even Xiao Han himself only felt some discomfort for an instant.

But that thing in his heart soon gave Xiao Han visions, and the first one is of a cultivation method which allows Xiao Han to absorb damage to enhance his body. A perfect cultivation method for a “walking target”.

- Description from Novelupdates

In a world fraught with innumerable dangers where living day by day is a struggle, a young man from the modern age transmigrated into such a world, accompanied by a peculiar system made for assassination.

Thanks to the so—called God, I somehow ended up as Uchiha Itachi’s younger brother and Sasuke’s twin.Wild, right?If I had to sum it up, I’d say, “Losing Shonen Jump is one thing, but losing your integrity? Now that’s a tragedy.”But let’s be real—none of that matters when you’ve got the Gojo System from the get-go. Yeah, you heard that right. From the moment I landed in this world, I was set to flex on the entire ninja world.And just like that, Konoha got itself a brand-new, utterly bizarre Uchiha.

Humanity has been gradually transported to the Abyss by a bored god to compete against other races and monsters.The problem is… humanity failed. In a last desperate push the strongest survivors chose a comrade to travel as far as possible back in time.