Tsukina Sasagiri, a green-haired young woman with crimson or amber eyes, initially operates as mission control for the hacking collective Steppenwolf. Adopted into the protagonist’s family after their shared father’s death left both orphaned, she grows up as their stepsister, entwining their fates. When Steppenwolf collapses post a disastrous operation, Tsukina enlists with the paramilitary organization VSS as a pilot, determined to transcend her perceived inferiority to her prodigious sibling.

Her past includes shadowy childhood involvement in neural-enhancement trials, a history less defined than her peers’. VSS’s brutal “special training” amplifies this vulnerability, weaponizing mental manipulation to strip her autonomy, reducing her to Reika Tachibana’s hollow-eyed puppet. Only her stepsibling’s interventions can fracture this conditioning, sparking fleeting clarity.

Driven by rivalry and a need for validation, Tsukina’s thirst to equal her sibling blinds her to Reika’s schemes, propelling her into a brainwashed antagonist role. Her bond with the protagonist oscillates between fierce loyalty, tangled codependency, and situationally romantic tension. A tomboy with a knack for meddling in others’ romances, her core journey pits her against external control, clawing toward self-determination.

Her arc wrestles with fractured identity and tenacity, juxtaposing her hacker origins against her militarized present. Pivotal struggles include resisting synthetic obedience, grappling with parental loss’s scars, and reforging agency. Depending on branching narratives, her story concludes in either irreversible subservience or hard-won redemption through kinship.