It's not the leader of the demonic cult, it's the baby leader

The leader of the Demonic Cult, the greatest villainess, Heukcheon Biyeon, has entered the world of romance novels. She is now the adopted daughter of Duke Bathius, known as the descendant of the devil. There are seven tests to become the official successor of the Duke’s family. If she defeats her competitors and becomes the successor, she will inherit the Duke’s secret techniques.

“I’ll be the successor.”

Biyeon passes the tests using internal energy and martial arts that do not exist in this world. She aims to become the Duke’s successor and achieve the realm of life and death that she could not attain in her previous life.

***

But why are the Duke’s family members, who were once eager to kill her, acting so strangely?

“Your temper and cruel nature are exactly like mine.”

When did you, who ignored me even when I shed blood, start speaking so sweetly?

“Who dares to threaten the Duke’s daughter?”

That doesn’t sound like something the eldest son, who once threatened to kill me, would say.

“You are the only successor to the head of the family that I acknowledge.”

The second son, who was my rival and couldn’t stand me, is now acting like a puppy who wants to be praised.

I was just trying to steal the Duke’s family secret, so why is everyone suddenly obsessed with me? And why is the leader of the martial arts world, who was my mortal enemy in my previous life, now acting like the puppy I raised?