Kool_lampshades's manga / #dragon(5)

Daughter of duke and fiancee of crown Prince has her fiance stolen from her by her sister. So she sacrifices herself as a bride to the fabled "dragon king" (a totally sensible action to take). Turns out though, that the dragon is real. And he takes her on as a bride. He goes on to usurp the king of a neighbouring country, and they become the king and queen if said country. They plan to overtake the FL's home country, as they were really shitty towards her. The romance between the 2 MCs is a slow burn.

I have read very few manga/manhwa set in the modern era, but I like this. Dragon disguised as human for the purpose of killing dragon players makes friends with someone who is a dragon slayer but doesn't know her identity as one.