Rubelia Oukoku Monogatari: Itoko no Shirinugui wo Saserareru Hame ni Natta

Alois, a man who works as an imperial guard despite being a descendant of the royal family. Elina, a duke's daughter who used to be the fiancée of the crown prince, Gerard. Their destinies completely changed because of the crown prince one-sidedly annulling his engagement with Elina. However, due to the emperor's intervention, Alois is to return as a member of the royal family and wed Elina?! This is the story of two people who, because of their sympathetic natures, are toyed by their circumstances, but soon come to learn about love and how to nurture their feelings.

(Source: Overlap, translated)