The Remarried Empress

Navier was the perfect Empress and a masterful administrator and regent for the empire; however, she and the Emperor were not lovers, and the Emperor wanted a wife, not a colleague. And so, he sought a concubine and placed a secretly ambitious slave girl beside him. That was fine, as she was willing to allow him his concubine of choice… until Navier heard the Emperor promised the slave girl the Empress' position. After much agonizing, Navier decided to marry the king of the neighboring kingdom.

A popular web novel adapted to webtoon.