MTL - The Villainous Bosses Mentoring System - Chapter 163 No reason

A former police officer dies and is longing for a quiet and peaceful life away from the chaos. Reborn in a new world, he must navigate strange lands, unexpected challenges, and a chance at the slow life he always dreamed of, if he can survive long enough to enjoy it.

A Speedster in a Fantasy World

Yu Ziyou and Zhong Wan served different masters.

They had once been the closest of souls, and were the bitterest of enemies.

After losing the fight for the throne, Zhong Wan brought his two young masters with him far toward the borders for the sake of survival. He relied on the little friendship that existed between him and Yu Ziyou when they were young. He borrowed some of his personal belongings while also dropping various hints around which made everyone think that there was something intimate going on between them.

Given the Yu Clan’s powerful authoritative presence in the imperial court, this appearance of a close tie allowed Zhong Wan to live a much better life than before. As such, the stories he cooked up began to carry more and more weight.

As rumors of their lovely romance spread a thousand miles into the horizon, Yu Ziyou, who was located in the distant capital city, eventually caught wind of his deeply moving and epic love affair. In a trance, Yu Ziyou, who had been completely brainwashed for seven years, believed in them. He guessed something special really did happen between them back in those years…

- 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.