Summary

Nier: Automata opens with 2B and 9S opening the way for a future incursion into machine territory, working to clear out machine threats for the local Resistance. With help from Anemone and later Pascal, 2B and 9S defeat multiple machine threats. During their missions, they witness the birth of and later fight Adam and Eve, physical manifestations of the machine network who reveal that their creators were destroyed centuries ago. 2B and 9S also encounter A2, who is on the run from YoRHa. It is revealed that the machines are beginning to feel emotions and gather in groups, and some like Pascal's group have grown tired of fighting. 9S is eventually captured by Adam, who is killed by 2B. Deprived of his brother, Eve goes mad with grief and drives the machines under his command into a frenzy. 2B and 9S kill Eve, but 9S is infected with the machine's logic virus, forcing 2B to kill him. Despite his body dying, 9S's personality is saved in the local machine network, allowing his transfer into a new body and resulting in Ending A. The second playthrough follows the opening narrative from the perspective of 9S, offering new insight into the machines and Adam and Eve. 9S also learns that humanity has been extinct since the events of Nier aside from a server on the moon holding humanity's DNA and history. YoRHa and its mission were created to keep the androids from losing morale. He also encounters a glitch when performing a standard server sync, and halts the procedure for both himself and 2B. Defeating Eve once more results in Ending B.