According to interviews with the developers, the world of Final Fantasy Versus XIII that exists within the last city to control the Crystal, as well as it's culture, is directly equatable to ours. The world outside the city, on the other hand, is much more medieval, and outsiders wage an ongoing war against the city and its residents. Their goal? To take control of the Crystals, and thus control magic.

Final Fantasy Versus XIII has been described by the developers as the 'shadow' to Final Fantasy XIII's 'light'. In essence, Versus could not exist without XIII's story, even though it has been specifically stated that the two games do not take place in the same world or society, and even though both stories share the same creation mythology based around the Crystals. In fact, the trailer for the game opens with a line from Hamlet, Act II, Scene II: "There is nothing either good or bad, but thinking makes it so."

The themes of the game have been stated to be "bonding", "friendship", and "sleep". Character designer and director Tetsuya Nomura has stated that Versus is perhaps the darkest, most tragic Final Fantasy ever, because it is simply the only way the story can be told.