Heretic Doctor Useless Consort - Chapter 19: The Beautiful Prince Blocks Her Way

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

Jin Runcandel is the youngest son of the greatest Swordmaster. After he gets himself kicked out of their clan, he meets a tragic fate…but before he dies, a God gives him a second chance. Now he must use his new power for good.

This story is centered around the man named Yi Ji-Hyuk, who has spent 1000 years in a Medieval Western fantasy-like world before returning back to the modern-day Earth. When he returns, he finds that his home is facing monster threats, and that humans with superpowers have appeared to protect the innocent people of Earth.