The sky-faring explorer Naia and her automaton companion Mano set out to investigate the Tower Shrouded in Mist where the sun was said to have fallen. Their airship is damaged so they decide to explore the interior while making repairs. The tower reveals itself as a vast ever-changing labyrinth teeming with bizarre monsters and vengeful spirits. Naia is soon captured by a laid-back yet ruthless ghost maiden named Mary who controls the dead and shows no mercy to intruders