Episode 21 marks a turning point where the carefree tone abruptly shifts into a grim, relentless struggle for survival. After a brief respite, Pascal and A2 receive an urgent message from Lily: The resistance fighters' camp has been infected by a virus from the machine lifeforms, turning the android fighters into violent zombies. In her desperation to contain the infection, Lily is forced to eliminate her own comrades, while the arrival of Jackass brings a fleeting moment of hope. Despite all odds, Lily and the remaining fighters decide to make one last stand, ordering Devola and Popola to flee with as many survivors as possible.

Meanwhile, 9S completes his mission to unlock the main tower and defeats a bizarre, clown-like machine lifeform before discovering 2B’s abandoned flight unit. A heart-wrenching video from 2B deepens his grief and drives him to destroy the core until he collapses from exhaustion.

When A2 and Pascal arrive too late, they find Lily on the verge of succumbing to the virus. She reveals that the infection was spread by the machine lifeform children they had sheltered. A2 comforts Lily with a final farewell, allowing her to die peacefully as "Freesia," her true name. Pascal discovers that the children he protected, driven by fear of loneliness, have turned into cannibals. In a tragic act, Pascal allows himself to be infected and begins self-destructing.

As the few survivors—Devola, Popola, A2, and 9S—grapple with the devastating losses, the stage is set for a final confrontation. A2 and 9S, driven by opposing motives, are on a collision course, but communication between Pods 042 and 153 hints at possible intervention to prevent the clash.