A majority of civilization was destroyed beyond repair when a world wide war swept the surface of the planet. Surviving people gathered as much as they could on different spots of the world, trying hard to survive in the barren wastelands.
Fidelis was founded by a group of people lead by former government officials. They had a batch of soldiers by their side, and a secured old capital of a fallen nation to use as their base of operations. Thanks to the choice of positioning, they were able to quickly recover pieces of technology crucial for survival.
A century or so of prosperous time passed, but everything changed when the robots attacked. Taking various shapes and sizes, these tools of war shot people down mercilessly. While Fidelis' territory was considerably wide before the robot attacks, the nation had to retreat their line of defenses as stronger robots started to appear.
Ever since the appearance of hostile robots, Fidelis declared war against those metal foes. Their main focus now is to hold on to their current territory, destroy the source of enemy robots, and hopefully, find any technology that could help them in their crusade.

The people of Fidelis are survivors of the wasteland. Life out of its borders is deprived; dire. Robots roam out of the woods every often, and the polluted lands are not suitable for growing anything edible. Not to mention the scarcity of wild animals. The only protection is your own weapons and the occasional Sunderer patrol.
Inside the borders of Fidelis, the recovered technology allows them to maintain much cleaner soil and water supply. The defense forces provide security, and robots hardly appear within the borders.
While technically there is no solid hierarchy, there does exist an unspoken ranks among the people. The descendants of the government officials solidifed their own positions in the Council of Fidelis. It is simply impossible to get a seat in it unlesd you have a connection to any of these "nobles."
Soldiers, Sunderers, ones who are recruited to take up arms against external threats, come second. Their life risking labor is acknowledged across the nation, and they gain respect from other people for their service.
The rest of the people come third-farmers, technicians, doctors... any who is not a "noble" nor a soldier.
There is no specific general discrimination against people with animal characteristics(or in professional terms nekomimis(catgirls) and such),as they had existed alongside ones without those features. It's just seen as a personal quirks.

The 'prototype' of Sunderers was a military division specialized in fighting robots, using the remainder of old military techniques. While it proved effective against squads of smaller variants of robots, it started to prove ineffective against more diverse enemies, along with a lack of fire support(modern air forces were no more, neither did they have much air vehicles in possession). With their limits, a much more... "anime" techniques proved effective in combat.
So came the Sunderers, taking up stylish weapons and fighting more like comicbook characters than soldiers. The government of Fidelis uses war propaganda style recruitment ads to recruit young people to the order.

Aka "How did all these anime girls end up here?"
You can't sign up to this institute of Sunderer Education just by signing up. You have to prove yourself worthy of such a glorious title-a basic examination of health and intelligence is done.
After that, the ones who passed the examination go through a field test, put to combat against robot minions with only the basic of gear to test their skills. The survivors of this deadly three day camping in the wilds are finally allowed in.

As far as you keep the power level to a personal level-no building wrecking, sun summoning, giant energy beam shooting, thunder striking wizard thrashers- I will allow most forms of powers. Please refrain from making one shot powers. What's the fun in that?
Powers existed for a long time. Probably before the apocalyptic war too. There's things like powers you are born with- stuff like shooting fire from your hands- and powers you can learn, like magic. So you can make a magic casting guns blazing anime girl with a dragon horn. Or something like that. Fun times.

I never specified "races", did I. Well, getting straight to the point,you're all humans. No elves or dwarves or anything. You're a human with related characteristics. You could turn into a giant wolf, howl at full moons,but that'd mean you have werewolf powersnkt that you are a werewolf race member thing. So yeah, that's that.
Think My Hero Academia if you ever watched that anime/manga.

Some 19 years old anime girls can destroy buildings with a flick of a finger. Some are mastermind fighters with intense neon green hair. Or even glowing hair. Or no hair at all.
That could be the case here too,but...
If you read the Also, Regarding Powers tab you would know that I'd prefer not too much of a super powerful character. You can be Stylish, but not Smoking Sexy Style. In understandable terms, your peeps just entered basic education for Sunderers after all. This isn't the endgame. Please keep that in mind.