I'm a Villain, but I Saved the Female Lead

I transmigrated into a novel as the villainess Rubelina, whose hopes of marrying the Crown Prince were dashed by the heroine Yvonne. I believed I could live happily as long as I stayed out of the love story between the heroine and the hero, Zilart. I lived my life without caring about them at all and as a result, the heroine and the hero became engaged without any trouble.

Thinking that my role was over, I was living peacefully when suddenly Yvonne came to visit me and blurted out:

"I want to break off my engagement with Prince Zilart!"

Um... in the novel, Rubelina is supposed to be the villainess, and Yvonne is supposed to be the heroine who lives happily ever after, isn't she...?