The Eldest Princess Arrives

In the modern era, she had no worries about food and clothing, but for no reason she traveled to the country of Nu Zun, which had no record in history, and she was actually the queen's biological sister. Why did it hurt me again and again? What is the reason for making myself invulnerable to all poisons? What is the reason for letting myself pass by death again and again... Everything is actually to cover up a shocking secret. What role do you play?