Martial King's Retired Life - Chapter 83Book 15:

10 years ago, after “the Gate” that connected the real world with the monster world opened, some of the ordinary, everyday people received the power to hunt monsters within the Gate. They are known as “Hunters”. However, not all Hunters are powerful. My name is Sung Jin-Woo, an E-rank Hunter. I’m someone who has to risk his life in the lowliest of dungeons, the “World’s Weakest”. Having no skills whatsoever to display, I barely earned the required money by fighting in low-leveled dungeons… at least until I found a hidden dungeon with the hardest difficulty within the D-rank dungeons! In the end, as I was accepting death, I suddenly received a strange power, a quest log that only I could see, a secret to leveling up that only I know about! If I trained in accordance with my quests and hunted monsters, my level would rise. Changing from the weakest Hunter to the strongest S-rank Hunter!

As the future High-Ranking among Elven, I was meant to be dignified and holy—but my friends never gave me the chance. One is a human prodigy turned “cripple” after an accident, determined to prove everyone wrong. Another is the Demon King, whose idea of preparing for war involves turning his entire race into farmers. As I watch my friends stir chaos in their own ways, I can’t help but wonder—how did I end up in the middle of all this?

In the territory of Zhao State, there are Liuxuanmen of the martial arts sect of Jianghu.

Su Yu became a handyman disciple who was just getting started.

Having obtained the sign-in system, he signs in at different places every day, and there will be various rewards.

Sign in at the center of the training ground and get the reward [Jiuyang Zhenjing]!

Sign in on the cliff near the residence of the handyman disciple and get the reward [Millennium Snow Lotus]!

Sign in in front of the sect library and get the reward [Lingbo Weibu]!

…

In this way, it was not until decades later that Su Yu discovered that he seemed to have surpassed the peak of martial arts and reached the level of cultivating immortals before he knew it…

Ninety-eight years later, a martial arts devil who was born out of nowhere made waves in the territory of Zhao, and no one in the martial arts world was his opponent.

Until this day, the martial arts devil killed Liuxuanmen and met Su Yu who was sitting outside the library, basking in the sun on a rocking chair…

- Description from novelbuddy

Beings that create and control monsters and demons, beings that build and reign over malicious labyrinths, the chosen individuals to possess an overwhelming Unique Skill… They are the Demon Lords.