Trapped in a Book, I Uncovered the Mastermind's Game

Transported into a tragic novel as a doomed fake heiress, she schemes carefully to survive and wins the favor of a powerful regent. Just as her path seems smooth, she digs up a modern mineral water bottle from an old well, shattering her understanding of reality. She discovers the regent looks exactly like a gloomy colleague from the modern world who once liked her. As the truth emerges and roles of hunter and hunted reverse, she vows to break free from this cage and make the real mastermind pay.