NieR: Automata – Devola and Popola

Temporarily removed

Even though Devola and Popola are returning characters from the original NieR, they’re different models from the Devola and Popola we see in the sequel.

To keep it short, NieR is about saving humanity from being wiped out, but Devola and Popola failed their mission, meaning the end and failure of Project Gestalt, and leading to the extinction of humanity.

The whole line of twin androids gets eliminated in result of destroying humanity, except for one pair - the Devola and Popola we meet in NieR: Automata.
Being resented by the androids, they're forced to do dangerous tasks, despite the fact that they're not combat models. They're even subject to verbal and physical abuse.
For me, the saddest part about the twins suffering is how their memories were wiped, and their systems programmed to generate constant feelings of guilt and remorse. This is why they accepted all the abuse, saying that it's their way of atoning for past sins, despite not being the actual Devola and Popola models who doomed humanity.