Half-brothers called "Princes of the Devil" -brother Sherabach and brother Astrod. The younger brother, whose soul is sealed in the body of his beloved Princess Nasiera by his brother, tries to call "Knight of Light", the only person who overthrows his brother, who is a dark person different from humans. However, on a knight-searching journey, Lucia, a young man who knows the former Nasiera, appears. Lucia is attracted to her while wondering about the changes in Nasiera. And finally, the love and hate of the dark brothers who give and compete for each other will reach the final moment.