I once heard Jim Sterling say, in one of his videos, that Nier Automata might be one of the most important games in gaming history, and I can see why. This is a sort of extended post thing from my first impressions post, and this is me just discussing the full game, its endings, and how it royally fucked me in the head. And I will try my best to explain this in a way to compel you to buy and experience it for yourself. That being said, however, this is heavily spoiled stuff, so just don't read on if you don't want to know all of the major plot points.
As stated before, you play as an android of the YorHa called 2B, joined by her partner 9S, and they are tasked with ridding the world of the machines that supposedly drove the human race to near extinction. At some point, you run across a couple of android look-alikes named Adam and Eve (Weirdly enough, they're both male and brothers), and become the main villains after 2B and 9S learned that the aliens who created the machines died out long ago. As a result, most of the machines have been cut off from what's been referred to as the Network, and began their own societies, such as one that lives in pacifism. How it works is each biome populated by machines run by a different aspect of humanity. Since the machines have no overseer directing them, they have no sense of purpose, hence they decide to adapt the emotions of humans. The desert area is populated by machines who live from love and family. The forest on loyalty of a higher power that does not exist. And the amusement park on self entertainment. The machines living in pacifism represent those who seek development and are the most curious, lead by a machine called Pascal. At some point, 2B would meet acquaintance with Pascal, leading to 2B feeling sympathetic towards them and seeing them as more than just one minded killing machines. During a job helping the resistance to transport a giant fuck off missile, the transport is suddenly attacked by a giant fuck off machine, with the two android barely able to destroy it with said giant fuck off missile. In the middle of the scuffle, however, 9S is captured by Adam. (( continued in comments ))