Ash, a young man who excelled as the captain of the Imperial Knights and was engaged to a noble lady, lived a perfectly smooth, enviable life.

However, one day, he was abruptly informed of the annulment of his engagement and his expulsion from the Knights. Disgusted with everything, Ash left the Empire and journeyed to a new land: the Kingdom of Rosebel.

In this kingdom, which has achieved prosperity surpassing the Empire through the power of Dungeons, Ash makes a fresh start as a Hunter, rapidly gaining renown for his overwhelming strength. Meanwhile, back in the Empire, Ulka, a junior who greatly admired him, follows Ash's trail and heads for the Kingdom.

The curtain now rises on a tale of reversal that will repaint his gray life.