Stuck in a dungeon for 5000 years and acquiring unimaginable power

Yoo Sung-ho was an outcast. Not because of him being smaller or weaker than everyone else, but because he didn't put up with their shit. He hated lying! He was always very outspoken and honest about everything.  One day he made the wrong person mad... and that person chose to get rid of him. What happens when Sung-ho gets trapped in a dungeon for 5000 years? What happens when he leaves? What does life have in store for him? (I will also be posting on royalroad.com)