MTL - After Crossing, I Marked the Empress - Chapter 13 Running for the Guard

In the foreign world, the martial artists dominate the world and the sword of the emperor controls the fate of hundreds of millions of lives! Long Yu, the number one killer on Earth, after dying, takes rebirth in this new world in an aristocratic family of martial artists but faces rejection because he is unable to practice martial arts.

- Description from Novelupdates

During a party one evening in the royal palace, Rachel, the eldest daughter of Duke Ferguson, was reproached by Prince Elliot for sins she didn’t remember committing and their engagement was abandoned. Rachel informed everyone she had not committed the acts they were accusing her of, but she was dragged away out of the party venue and thrown into the palace dungeon.

She was originally an assassin. After rebirth, she was reduced to another world’s Di family’s most inferior concubine-born daughter. With an extremely hideous appearance and no way to cultivate, she was the object of everyone’s humiliation and bullying.

A back-to-basics(?) monster evolution novel.