In Atelier City, an artistic haven filled with technological marvels, lies a netherworld where monsters dwell. These monsters embody the dreams of humanity, their greatest hopes and worst fears. Stumbling into this netherworld by accident, Allen Lee, an ordinary young artist looking for wonder, encounters an odd woman said to be a potential inheritor of the title, "Grim Reaper".  Caught in a battle of succession he was not selected for, Allen struggles to learn magic in a society where people possess it innately while the Reaper’s Inheritor vies to escape the chains of fate binding her. Seeking to find a treasure that can rid them of the curses they are dealt with in the midst of this, the two become amateur supernatural investigators collecting mystical art pieces left behind by the monsters they find. With eight others who are potential inheritors to the Grim Reaper who have been foretold to become legendary heroes deciding to unleash the threat they were meant to vanquish, can an unchosen one and one chosen for darkness defy destiny itself?