In year 2000, a catastrophic event known as the Second Impact took out half the world's population and melted all the ice in Antarctica. According to the UN, it was a giant meteorite, but there were many rumors that said otherwise.
It is now year 2015. Mysterious entities called Angels started appearing,
causing mayhem to the remaining population. All conventional weapons proved
useless against them, including the UN's key weapon, the N2 bomb because an AT
Field (Absolute Terror Field) protects the Angels. The only weapon that can
penetrate the AT Field is called the EVA, which is developed by an
organization called NERV. EVAs are biologically based giant humanoids, which
requires the control of a pilot by synchronizing the pilot's mind with it.
Thus, the pilot's senses extend into the EVA unit. Every thought, feeling and
action is automatically executed by the EVA (and vice versa!!) Only a select
group of children born after the Second Impact have the capability to synch
with an EVA.