Jack acts as the loyal enforcer and second-in-command to authoritarian leader Izamura, executing orders with unquestioning obedience. Clad in a black uniform, gas mask, and red-lensed visor, he oversees security operations, enforcing Aiga’s rigid laws and capturing perceived threats like "Inverts" to bolster the State Sec’s fearsome reputation.

A turning point emerges when Jack defies orders to save his trapped subordinates during a structural collapse, revealing his capacity for moral autonomy. This defiance sparks suspicion toward Izamura’s motives, prompting Jack to investigate. He uncovers Izamura’s role in murdering Age’s father and imprisoning Lagos—crimes central to perpetuating the regime’s fabricated history.

These revelations drive Jack to ally with Age and Patema’s group, aiding their mission to expose their societies’ interconnected pasts. He joins the climactic showdown, helping thwart Izamura’s attempt to eliminate Patema. After the artificial world’s collapse, he partners with the underground Elder and Porta, pledging to unite the divided communities through cooperation.

Jack’s journey evolves from blind obedience to defiant resistance against the regime’s tyranny, driven by the need to atone for his past role in state violence. His arc mirrors broader themes of redemption and confronting systemic indoctrination.