The Abandoned Queen: Luckily, My Divorce was Finalized. Once I Left, I Found the Crown Prince of Dragonia Waiting for Me.

Rosalia, a talented magic tool developer, is chosen by royal decree to become the queen of the crown prince, Wilbert. For the sake of her beloved family and people, she has supported her country from the shadows. However, Wilbert, who is obsessed with his concubine, declares he has no intention of loving Rosalia. After six years of being ridiculed as "the princess who nobody loves" in a sexless marriage, Rosalia's life as a queen in all but name comes to an abrupt end when Wilbert's concubine becomes pregnant. She is ordered to divorce... but Rosalia's heart is as light as a feather as she finally achieves her freedom! She then decides to leave the kingdom with Ares, her butler, who has been by her side for many years. With Ares' suggestion, they head to his homeland, which turns out to be the Kingdom of Rakteus, the home of the Dragonborn, known only through books of old. The Dragonborn are said to possess knowlege beyond that of human understanding, and to have a single "mate" with whom they stay with for life. Rosalia easily accepts that the mysterious Ares, who possesses enormous magical power, is a Dragonborn, but it seems that he has other secrets as well...!

(Source: MangaPlaza)