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. Allen Lee, an ordinary young artist, stumbles into this realm by accident. He soon encounters an odd woman said to be a potential inheritor of the title, "Grim Reaper".

Discovering that a group of chosen heroes of the netherworld have sided with the threat they were meant to defeat, Allen and the Grim Reaper’s inheritor decide to confront them as a team of part-time supernatural investigators hunting down mythic entities and prophetic art pieces that may be the key to solving their problems. However, can an unchosen one and one chosen for darkness go against heroes guided by fate itself?