Since When Were You the Villain?

She transmigrated into a book without knowing what novel it was. Then, one day, her fiancé appeared. Killian was a perfect Northern Duke with black hair, red eyes, and a handsome face. It was a contract marriage.

"He is obviously the male lead." So, Sophia believed this without a doubt. She thought he would be the male protagonist. But...

"Ah, I got caught." The smell of blood brushed against her nose. Killian's eyes narrowed. Then she realized the fact that he was a villain, and a cold hand caressed her cheek. Raising the corners of his lips slightly, he whispered softly, "There won't be a breakup, Sophie."

Wasn't this a trope? She absolutely abhorred this type of plot twist.

(Source: Kakao Entertainment Corp., translated)