The Dark Lord Revenge

My name is Roy Darkness!
I was used to be the weakest of my village.
But one day I've awaken a strange analysis skill.
From that moment I began to train harder to gain more power.
And one day I've become the best strategist of the humans' land.
Then the king convoked me to help the prince to defeat the demon lord.
I accepted and we went through many battles and I thought that I was his friend.
But the night before the final battle the prince betrayed me and triedvto kill me.
After his return he was called the hero who defeated the demon lord and It was told that I was a coward who tried to run away during the battle was killed.
Now I seek for revenge.
Now I'll tell you what happened and how I took my revenge.
The story of the Dark Lord Revenge
The one who took over from the demon lord.