Van Gogh Reborn! - Chapter 220:

Thrown into a brutal world of swords and sorcery, his memories stolen by an unseen force, Magnus wanted only one thing: to go home.But every kingdom, devil, and god — along with regressors, possessors, and fellow reincarnators — seeks to carve him apart.Survival demands war. War demands survival.And with a System that hides more than it reveals, Magnus is dragged down a bloodstained path... one battle, one betrayal, one broken world at a time.

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.

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.

A martial art expert from the Song dynasty lives like a Phoenix that can live again in another body after death. This time, he happened to take over the body of a Japanese high schooler who is also a victim of bullying and has a bit complicated family circumstances.

- Description from Novelupdates