Feels like Eureka 7.
And a bit of King Gainer.
So its a kid's live changes as he mutates than joins some postal company?
School life then explode to full scale wars and earth conspiracies.

Theres the white haired girl and the red haired girl (with face marking like the old lady in the pre-op)
Eureka candidates?
Just love to compare. :P

Got that high tech old time feel.
Some weird earphone Akiyuki had on.

Ok, I don't understand the war part at all.
Is the island supposed to be a "Heliopolis"?

What is the motive of this "terror" attack?
How many monsters will appear?
Suppose most will be from those students?
So white haired girl just go boom.
Guess not.

Woah, cool henshin.

Feels like beneath this messed up world something else is happening...

Cool OP.
ED makes the red-haired girl very lonely.

Some thoughts:
Who are the white haired people?
What is the green thing?
Whats that nut thing that changed into something else in the green solution?

===================

Ok I suppose those nuts grow into monsters.
That ring looks similar?
Not really mecha but organic.

War started...again?

Enter..Fishman!! :P

One of the scientist in the OP has the face markings too.

You get to see all sorts of nifty gadgets in anime.

A completed Xam'd?
That stick sure is powerful, one stab and its effective.
Looks like a blood clot or maybe rust.

The red-haired girl knows stuff.
Tell us more!!

That card game looks like UNO.

So we have Eureka and Renton :P

What is the typography we see in the op and the between part A/B scene?
An original typography used by the white-haired/face marked civilisation?

Northern Government? So theres a Southern Government?
Is Sentan Island on the equator?

Cool! Voodoo doctor feel!
Looks like Humanform weapon is widely used.
So far everything is sudden and unexplained.

That animal reminds me of the one Anemone had.

So the Northern Army has a face marked and a Xam'd too.
That commander reminds me of Dewy.

Hinting the past of the red-haired girl?
The commander has the same habit as the violent female captain(Ishu, is it?)
Siblings? Like Dewy and Holland?