Umm, anyway. Back to the story. So 500 years ago a massive war of near extinction breaks out. During the later stages of the war, a discovery is made wherein it's possible to inject nanomachines into virgin females and have them manifest 'robes', which are basically just battle armor with accompanying weapons. Even without the robes the nanomachines provide a physical boost and a minor healing factor but it's the robe that really womps ass. With it the Otome (maiden in japanese) can fly, has super strength, can manifest energy shields, can shoot ray beams, and basically kick ass. This first Otome used her power to bring the war to an end, you can assume by kicking ass until everyone took their toys and went home. I imagine the survivors gathered around the negotiation table, looked at the absolute destruction, and came up with a new world order meant to avert any further world wars. The first step was they decided to abandon technology over time. The truly scary stuff was locked away and tech as a whole was slowly bled away from society. Second, they opened up a school to train more Otome's. BTW, the reason that the Otome's are 'maidens' and have to stay that way is that semen has an antigen factor in it that disrupts the nanomachines and once an immunity develops it's bye-bye superpowers. Someone commented on another forum that this is just asking for some sort of anti-otome bukkake squadron to be developed. I digress though.
At this point, it was decided that the school would accept girls from all over and if they had the talent and ability, train them to be Otome's. When their training finished, they would then be allowed to go back to the country that sponsored them and serve the nobility/royalty as master. The rub of this is that the Otome and master are linked and whatever harm suffered by one is inflicted upon the other. If one dies, so does the other. Because the Otome were so unbelievably powerful compared to the conventional weaponry that was left around, peace more or less came to the planet as a whole.
Now, what bothers me is that this sounds like the stupidest idea I have ever heard in my life. My first thought upon hearing this setup in the anime is that whoever came up with this has got to be the most naive and witless moron ever born. The first metaphor that came to mind is it's as if the when the United States finally invented nukes and ended WWII, they immediately decided to invite the scientists of all the other countries to come on over and learn the technology so that everyone could then live in peace and happiness. WTF?
The fact that each Otome was only loyal to the royal family of the country they came from makes them nothing more than walking weapons to be used by that country. Not to mention the fact that their very life is now joined to the head of that country so they've got a good incentive to kick ass if conflict ever did break out. It's made even worse in that in their training it was stressed that their first loyalty was to their eventual masters. No attempt was even made to have them hold their highest allegiance to the institution of Otome's that was training them. Not that that would have worked in the long run either, mind you, but it might have helped a little to mitigate the treachery. Of course what ended up happening is 50 years or so before the main series all out Otome war breaks out and if it's better than the first war that nearly wiped out civilization, it's only because there are fewer Otome's around than nukes or whatever they were using back in the day. Instead of trying to fix the problem by say, reorganizing the system so that you don't pass out little girl nukes to the nobility of each country, they simply cross their fingers and keep the status quo.
Maybe my real problem with this setup is that it's so idealistic it makes me want to vomit. Maybe they wanted to give Otome's to all the various countries to show that the school wasn't a threat to them and so Otome's could be integrated into society. That might be nice in theory but it's completely asinine and will never work when you mix in human nature. It might be more 'evil' or Machiavellian but given the same circumstances, I would have created a totally separate entity which kept all the Otome under my own control. They would be taught their first loyalty was to the school and if any other nation stepped out of line they would have a dozen power-ranger Barbies kicking their ass with giant ray beams. Hell, maybe this idea would just end up building an evil empire all its own but at least it would be a strong and stable one.
It's amazing how often in fantasy this sort of thing comes back to bite you in the ass. I was trying to think why this entire setup in the anime bothered me so much and I think it's because I've seen the same thing turn to ashes so many times in fantasy novels. There's always idealistic king or ruler who decides after a war to forgive his enemies and brings the sons or daughters of that enemy in for advanced training in magic or combat or whatever, thinking that it will promote understanding. What it ends up doing is training up the new dark overlord who will turn out to be especially skilled at soaking up all that knowledge and skill you're offering and then go back to his country where in a few years he comes back with an army and stomps you flat using the very tools you gave him. There's probably a lot of practicality in just killing your enemies and any children/pets they have and just nip it in the bud. Even if you feel the need to be benevolent, there's no freaking reason you should hand out weapons that can so easily be used against you.