Summary:
Lang Byul, the shy and kind-hearted third son of the Seong Yul and Lang families, was a young man expected to grow into a strong and talented warrior. However, everyone later discovered his lack of talent due to a prophecy. As a result, he was abandoned by everyone, even by those closest to him, which drove him to run away in search of a way to change his weak personality and find what he truly desired.

Following his aunt’s recommendation, he settled in a small isolated village, where he met an old man. He later discovered that the man had been a skilled swordsman from the Seong Yul family, who helped Lang Byul become the person he had always wished to be.

Before his death, the old man’s final wish was for Byul to swallow the “Legendary Pill.” In truth, Byul swallowed it moments before being killed by his own brother, only to find himself returned to the age of fifteen. Determined to make his new life exciting and free, he focused on reuniting with his friends, repairing his relationship with his brother and family, strengthening himself, and enjoying every moment of this life.

However, an evil spirit entered his body, claiming to be the Emperor “Cheonma” — the mad, bloodthirsty emperor who built his throne upon skeletons, a name that alone terrified even other emperors. Lang Byul did not believe the spirit, assuming it was merely a ghost obsessed with Emperor Cheonma, until it disappeared from his body five months later.

When the day of the “Sword Selection” arrived, he was chosen to wield the “Great Seong Yul,” the Sword of Absolute Destruction. It was the same sword he had carried in his previous life, but now it had awakened. The priests even accused him of using a forbidden spell, yet that was not the most important matter.

The truly important moment was this: a handsome man with crimson hair and shining red eyes sat before him — Emperor Cheonma himself. Standing before him was Lang Byul, who, according to the traditions of joining the family, was required to dance before him.

“But why does this man keep looking at me and smiling? Moreover, he protected me from the dwarf spirits’ attack, and now he wants me to become his disciple!” Yet who could have expected that the Black Blood Emperor harbored hidden intentions?     
( Note: I am also publishing this story on Royal Road under the username "Raya Dell".)

Chapter 15 - Chapter 15: Where is the etiquette of discipleship?