Some time after the 21st century, when mankind has left a wartorn Earth for the stars, a galactic government imposes a harsh entertainment ban. Many fight against it, including a group of idols who cross the stars to meet their fans: AKB0048.
Type: BlossomIn Stellar Calendar year 0050 something strange happened that no one initially took notice of. It was a normal day for every world in the galaxy, but behind the scenes the gates had opened, connecting their vast world to myriad others.
Though initially nobody seems to have become aware of the fact that there is a much larger universe out there waiting for them to explore, it is only a matter of time when that happens. What will happen when it does is anyone's guess, but given the overwhelming presence of the DGTO it would be a safe bet that the many corporations that compose it will attempt to exploit this change in their world for their own personal gain. Perhaps they will launch expeditionary forces out into other worlds, looking for new places to harvest resources from, just as they strip mine whole planets in their own world. Perhaps they will be diplomatic. In truth it will likely be a little of both, and given that the Harvesters and the DGTO have similar interests, the various worlds of the Tree might be in for some trouble if they should actually meet one another. But just as the DGTO will be there for their own interests, the EPS will also be there to bring hope to new worlds and fight against oppression in all forms. Just as the various planets already part of it came together through a common goal of freedom and hope for all, it can only be assumed that the EPS will welcome any other political bodies that share similar ideals-it will likely have to to ensure it can continue to defend the ideals it was formed on.
As things stand, the galaxy sits near the beginning of Stellar Calender year 0050, two full years after the end of the series. It's hard to say what exactly has happened between the end of the series and now, aside from the fact that Motomiya Nagisa became the 14th generation Maeda Atsuko, and three members of AKB0048 displaying the ability to trigger the Center Nova phenomenon. Any other developments are up to individual players so as to not presume upon others interested in apping into the theme.
There is some level of anachronism in the technology levels across the galaxy. In the core DGTO worlds, technology is definitely reaching into the realm of future tech, and there are quite a few planets within the EPS that are similarly advanced. But just as often you can find worlds where technology is at a level found in the early 21st century, and a not insubstantial amount of worlds with less than that, reaching all the way back to the time of the industrial revolution. It's no surprise that most of these worlds are mining worlds under the oppression of the DGTO.
The kirara are strange creatures that appeared from hyperspace after the first ship entered it. They appear to be completely harmless and luminous creatures that are attracted to brilliant souls-perhaps gaining sustenance from them. They shine brighter the more a brilliant soul near them shines and seem to not harm anyone they become attracted to (after all, every member of 0048 has a personal kirara). They are capable of generating shields of energy that can serve as protection in one direction and are capable of stopping most kinetic impacts. It has been shown that a sufficiently strong impact (such as most high explosive weapons) or sustained weaker forces over a short period of time can break the shield. But regardless of what they are capable of, they are adorable, playful little creatures that seem at least somewhat intelligent and appear to have some connection to 0048's rites of succession for members.
A rare element discovered long after humanity abandoned Earth. It has many unique properties to it that make it both sought after to alloy with other elements to create stronger materials for building. However its most unique property is how, with enough energy pushed through a sufficient amount, it can open gates into hyperspace and allow for swift bridging between stars, turning trips that might have taken thousands of years into a few days to weeks at most. It is extremely difficult to mine though and almost all known worlds with it are under DGTO control, ensuring that the corporations that compose it hold a monopoly on FTL travel outside of the EPS. Even a few grams could make a man rich beyond their wildest dreams.
This strange phenomenon is brought about by particularly radiant souls which unite with the kirara and touch into a strange other world within hyperspace, granting those that call it down with myriad powers from the same sort of hyperspace travel large ships are capable of, to projecting their consciousness across vast distances to touch multiple people at once. It can also be used for defense, turning aside even the greatest of assaults (two such people were able to withstand the full force of a battleship's main artillery for a sustained period of time). It might even be used to enhance the physical aspects of a person, or alter the minds of others. The phenomenon is poorly understood at present. Currently there are only four people known who can bring about a Center Nova, though there may very well be more either waiting to show their radiance to the galaxy or who are hiding that radiance. It's even possible that people from other worlds could trigger the phenomenon. It is, however, extremely dangerous, both because it puts a great deal of stress upon those who use it and also because of the very real risk of a Center Nova disappearing, potentially forever-consumed by their own radiance.
It's very likely that there are many groups in the Entertainment Protection Sphere that fight against the DGTO, waging the same sort of war that 0048 does, though they've clearly not made quite the same impact or only work locally upon planets under the entertainment ban. It's entirely possible that there might be other groups like 0048 who are blessed by the kirara and even have their own rites of succession. Only time will tell if such groups speak up and make themselves known to the galaxy at large!
People who know the source material will probably realize that there are some things different here when compared to the actual series, and that's both to better integrate the theme with the rest of the game and also to correct what seem to be errors in the setting itself. For instance, canonically the DGTO imposes the entertainment ban to suppress idols who can make the kirara shine and activate kirara drives which are stated to be clean and efficient FTL drives. However later it's shown that the kirara drive is the same sort of dualium powered drive that all ships use, so this can't possible be the case. It makes more sense for the entertainment ban to be in place to control the populations of planets the DGTO uses to mine dualium (in so much as that makes any sense at all).
Another thing that might seem odd is the changes to the concept of the Center Nova. There is no such thing in AKB48 to base this on as there has never been a sole member that was always the center position in all performances. The center position has always changed (though it is true that Maeda Atsuko and Oshima Yuko were centers for a ridiculous number of performances). It makes more sense to simply say that a Center Nova is someone who can cause the Center Nova phenomenon. Going by that reasoning, at the end of the series, there would be four people alive that could be called a Center Nova: Maeda Atsuko the 14th, Sono Chieri, Minamino Mikako, and Oshima Yuko the 9th. This allows people out of theme to potentially also gain the Center Nova power and also neatly gets around the questionable idea of Chieri suddenly becoming part of the successors without actually succeeding a name. Therefore position 0 has no particular importance beyond being the position out in front during performances and all past and future Center Novas are those whom the kirara particularly favor. We can simply say that Yuko's goal was to shine brighter than any other Center Nova instead of the much less impressive desire to stand at the front of the stage all the time.