Erika Ainsworth, originally named Pandora, is an immortal crafted by the Twelve Olympians in Greek mythology over six millennia ago. Charged with opening Pandora’s Box upon humanity’s extinction, she remains unable to fulfill her purpose, as the box remains sealed within Miyu’s world—trapping her concept of death and cementing her immortality. Centuries of persecution by humans, who reviled her as a monster, forged her bitter hatred for humanity and desperate longing for death. Adopted by the Ainsworth family, she assumed the alias Erika, enduring a thousand years under the guardianship of Darius Ainsworth.

Outwardly cheerful and deceptively innocent, Erika wields lies and manipulation as tools, concealing a cunning, perilous nature. Her calculated decision to transfer Illya’s soul into a stuffed animal to evade Darius’ wrath underscores her ruthless pragmatism. Yet she harbors genuine attachment to Miyu Edelfelt, whom she idolizes as an older sister, and grapples with profound loneliness in Miyu’s absence. This duality defines her: a childlike yearning for connection clashes with millennia-hardened cruelty born of endless suffering.

Her identity as Pandora reemerges when traumatic events fracture her fragile psyche—most notably Miyu’s rejection of their bond. This triggers a mental collapse, worsened by contact with a cryptic “mud cube” tied to Pandora’s Box. The cube warps her body into a slightly older form, and her personality shifts to icy disillusionment. Embracing her Pandora persona, she openly pursues death to escape her eternal duty, allying with the Ainsworths to unleash the box’s corruptive mud, a force poised to annihilate humanity.

Pivotal relationships shape her path. Darius, her adoptive father, metes out harsh discipline for failures, yet she mocks him during his eventual downfall, shedding subservience for defiance. Her bond with Miyu fractures under ideological strife—Miyu’s refusal to acknowledge their friendship deepens Erika’s despair. Julian Ainsworth, Darius’ son, exploits her vulnerability, leveraging her link to the box to further his ambitions. This culminates in her symbolic “drowning” in the box’s black goo during a climactic clash.

The mud cube, revealed as Pandora’s Box itself, acts as catalyst and weapon. Darius’ opening of the box unleashes global catastrophe, freezing time moments before humanity’s extinction and entombing Erika beneath the mud. Subsequent timeline resets and battles underscore her tragic role, torn between duty and fractured humanity. Her final acts—sardonic taunts toward Darius and ambiguous exchanges with Miyu—leave her fate entwined with the box’s lingering power, unresolved yet eternally bound to its dormant threat.