World-saving Plan: The Only Savior - Chapter 68 - Unicorn Blood

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

This legend tells the tale of the protagonist, Kuroki summoned to protect the demon king from the hero.

Kuroki, unbeknownst to him, suddenly came to another world. He was summoned by the demon king, Modes. The territory which the demon king overrules was in the midst of being destroyed because of the hero. He had no choice but to bow before Kuroki.

“Please save us, Savior Dono!”

Kuroki nodded, deciding to save the demon king due to an unexpected turn of event.

Su Yu, who was idly passing his days in a third-tier university, ended up in a terrifying unknown forest due to the “Sinkhole” incident. His school collapsed into the “sinkhole”. The forest was filled with various terrifying mutations, which started, right in his hands.

This is a world where humans, demons and mysterious beasts coexist.

Humans cultivate mysterious qi. Demons cultivate corporeal bodies. Mysterious beasts cultivate soul perception.

A legend says that in the middle of an endless rainforest, there are extremely powerful existences; they are called demon kings.

Some demon kings have a tyrannical corporeal body, some are experts in illusions.
Some demon kings are proficient in magic, some can even move mountains.
Some demon kings are able to sense things thousands of miles away.

These demon kings rarely appear in the human world. Even if they emerge in the human world, they would reincarnate in human form; assimilating with mankind while seeking to breakthrough realms…

- Description from Novelupdates