In Episode 22, the story revolves around Devola and Popola. The episode begins with the twins narrating the tale of the original Devola and Popola, who were meant to oversee Project Gestalt—a failed program intended to restore humanity, which ultimately led to humanity's extinction. Popola deeply regrets that they couldn't protect anyone and wonders how long this regret will linger.

At the same time, 9S (Nines) attempts to enter the tower, but the door remains locked, even with the correct passwords. When he switches to hacking mode, he encounters an earlier version of himself—not just a copy. This past self guides Nines through various locations, revealing the corpses of his previous iterations. Nines realizes that 2B, also known as 2E, has executed him countless times as part of her mission. The past Nines hints that their repeated executions were meant to create the current Nines, who is an essential part of Project YoRHa's goal to achieve a new, unprecedented outcome.

After exiting hacking mode, Nines is attacked by hostile Machine Lifeforms (MLs) and is too damaged to wield his sword. Devola and Popola come to his aid, defeat the MLs, and repair his severely damaged motor cortex. As more MLs approach, the trio attempts to retreat into the tower, but only the Nines can enter. Devola and Popola decide to stay behind and hold off the MLs, atoning for the "sins" of their predecessors—the original twins, who are considered "great failures" for their role in humanity's extinction.

During the fierce battle, the eyes of the severely wounded Popola turn red, alarming Devola. They realize they cannot survive without each other, and it becomes clear that this might be the end of their journey. The episode ends with Nines entering the tower alone, the outcome of his solitary mission left uncertain.