Before the Fall: Rise of the Apocalypse King - Chapter 43: (dont unlock this ,its vol.3 chap)

A man was transported to Ancient China and eventually became a servant of a declining household without a male heir. He utilized his wits and modern knowledge to help the household and eventually become trapped in the sea of political turmoils of the period.

- Description from Novelupdates

Skyseal Emperor Gu Taxian is perhaps the greatest Emperor in all of history. He crushed the Hundred Empires and brought them to heel, built the vast Great Stone Wall to keep out the deadly wilders, relocated mountains and rivers to promote commerce, set up roads and highways, and even promoted free academies of learning for the common man in an attempt to uplift them. But the Skyseal Emperor’s ambitions involve more than just this – he is preparing to launch a great campaign to stamp out all pagan religions, wishing to allow all men to become like gods instead of merely worshiping them. Deities, demons, and immortals alike tremble and rage at the Skyseal Emperor’s ambitions.

He is the ruler of the mercenary realm, an overlord that gives headaches to the leaders of any country! For the sake of his friends, he’s willing to sacrifice himself; for the sake of his family, he does not hesitate to spill blood! He is a dragon, one that soars above even the highest of heavens. He’s a power that advances triumphantly through unstable situations, stirring up both the winds and the waters.

- Description from Novelupdates