MTL - Chongfei Manual - Chapter 10

The formless ancient world was infested with despicable demons. They hunted and feasted on mankind, keeping the human civilization constantly in a weak and suppressed state.

She, a genius abandoned by her clan. He, a proud, pampered, two-faced imperial crown prince, a developing supreme ruler of the world. She, tricking him, disguised as a pig to eat a tiger, suppressing him, provoking him. Every time, after playing with him and stirring him up, she’d escape.

No man could put up with this! He could only hunt her, pamper and indulge her, lure her into falling in love with him, who would have thought, the one to first fall in love would turn out to be him———-

A young man who stood above the world, a young lady who dominated the landscape, evenly matched opponents, evenly matched romantic game of chase and tag.

- Description from novelupdates

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.