Deep sea dark fantasy.
The bottom of the deep, deep sea, water pressure, darkness, low water temperature ... This is an unexplored, desperate place.

A combination of Libitina, a woman in a jet-black suit packed with lost technology, and Jack, a shallow-sea people, seeks ancient human relics (artifacts) and conquers the dangerous abyss of weak meat and strong food.

By evading the threat of humanoid monsters "ghosts" roaming the seabed and giant deep-sea creatures, they can escape from the "worst world" and be exposed to the warm "sunlight". Or ... !!