Nines continues his harrowing journey across the surface, forced to face relentless challenges. He reaches the mysterious white tower, only to be halted by a massive barrier. His encounter with Operator 21O, now a corrupted 21B, ends tragically as she sacrifices herself, transferring crucial data about the tower to Nines' space pod and urging him to do his best in her final moments.

Meanwhile, A2 finds herself back in Pascal’s Village, where she initially resists but gradually warms to the peaceful Machine Lifeforms (MLs). She is tasked with gathering materials and eventually takes care of the village’s children, revealing a softer side despite her usual disdain. When hostile MLs threaten the village, A2 and Pascal prepare to defend it, with A2 surprisingly fighting alongside the very beings she once sought to destroy.

As Nines begins his mission to decipher the tower, he enters the first subunit within the sunken ruins of the city. There, he mercilessly annihilates a regiment of dormant MLs, ignoring their pleas for mercy. Destroying the subunit’s core, which screams in a childlike voice, rewards him with the passcode "MY SIN," reflecting the growing darkness within him. With two subunits remaining, Nines’ resolve and mental stability are pushed to their limits the closer he gets to his goal.