When Elysia's twin sister Elyana is forcefully engaged to the terrifying Duke of North Cadmium, she does what any good sister would do: She swaps with her on the wedding day and attempts to murder him every chance she has afterward of course. But what happens when Duke Klein is nothing like the rumors say? Why is he being so nice to her? As Elysia starts to get close to the Duke and uncovers the mystery behind his terrifying reputation, she begins to question everything; while also dealing with her possibly real love for the man who wasn't meant to be her husband.