The Slime Grand Duke and the Downfallen Noble Lady's Surprisingly Happy Engagement

In our country, there exists a title called the "Grand Duke of Monsters," comparable to the power of a Duke. Long ago, this special title was bestowed upon the hero who defeated the seven monsters that plunged the continent into chaos. The title of Grand Duke of Monsters is inherited by the hero's bloodline. Becoming associated with a Grand Duke of Monsters is an honor. Having fallen from grace and unable to provide a dowry, I have received a marriage proposal from one of the Grand Dukes of Monsters. That man is the Slime Grand Duke! ...The Slime Grand Duke, you say?

The Slime Grand Duke, the most shadowy of the Grand Dukes of Monsters, wishes to marry me. First, we'll try living together before marriage. With my pet duck under my arm, I set off for the lake district, the territory of the Slime Grand Duke. I tremble before the imposing mother of the Slime Grand Duke, am surprised by the Dragon Grand Duke, His Highness Axel, who is somehow worried about me, receive various harassments from the Slime Grand Duke's second cousin, and am embraced by slimes, but I'm fine!! (Probably.) *Note: This novel has been adapted into a book!*