I already made an RP on the concept. On this site.

As the game is called Final Fantasy and not Final Sci-Fi, it would be set in a fantastic world (although there will be sci-fi elements, as explained shortly).

Basically, the main characters this time are all of the summons. Their world has been invaded by a group of highly technological and militant humans. Another group of humans who have some command over magic and technology also appear, and the story revolves around the war and politics of the three factions.