I Am The Young Master - Chapter 1 - Well... shit.

A skilled but unfortunate modern-day assassin was killed in a freak accident. However, he soon found himself summoned to another world by an evil wizard, who had him possess the body of a boy as an experiment. After successfully planning the evil wizard’s downfall, he used the wizard’s body as a springboard to gain influence and power in his new world.

- Description from Novelupdates

Everyone said that Yi Qing was the number one Sword Cultivator in the world, with a swordsmanship and cultivation that no one could surpass. Whether it was when he was cultivating in the Lower Realm, or when he was in the Ten Heavens of the Upper Realm, he has always been undefeated.

Anger. Pain. Desolation.

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.