Third-Rate Villain Of Fantasy Novel

What began as a childhood fantasy becomes a cruel reality when our protagonist awakens within a romance fantasy novel—not as the main villain, but as an insignificant antagonist destined to be a stepping stone for the female protagonist. His torment is compounded by one devastating fact: she's also his fiancée. When their engagement dissolves according to the narrative's design, he seizes the chance to vanish into obscurity as a forgotten side character. However, the female lead has other intentions, deliberately preventing him from slipping into the story's background.