Shin Chi-beom is a talentless amateur mixed martial artist.

After disappearing for a week, he suddenly shows up for his next fight, suffering from extreme anxiety, and steps into the cage and kills his opponent, leaving everyone wondering why he's changed.

A week ago, he fell asleep and woke up in ancient Greece, where he was a combat slave in the Pankration, a murderous martial arts competition. Five years of life-and-death duels, dozens of times a day, in countless battles, have passed...
After the final battle, he is returned to his original body.

Shin Chi Bum is left with severe trauma and a mental illness. The only place he can find peace of mind is in an octagonal iron cage. The only place he can find peace of mind is in a cold, octagonal iron cage. He continues to search for the strongest...

Will he ever find rest at the end of the fight?