In his world, everything except white is red, yes, the red of blood, a childhood tragedy, a fateful encounter. Xueda Riley and Allen Walker were both people who met the Millennium Duke. One was cursed by his beloved Mana, and the other was a person who almost became a demon and was "loved" by his father. When their lives are no longer just parallel, the story has just begun. This is the story of Allen, Xueda and Millennium Duke, the evolution of demons, and the evolution of exorcists. They have not only fight but also love.