Grete hails from a politically influential family where relentless emotional abuse centered on a prominent facial birthmark deemed disfiguring. Her father and brothers verbally degraded her, forging deep-seated appearance insecurity and a fear of men—especially loud or aggressive individuals—that often triggers physical discomfort. This trauma culminated in abandonment at a spy academy at thirteen, severing ties to family and high society.

The birthmark, resembling a burn mark, fuels intense shame, compelling her to habitually conceal it behind a mask. Despite this, she maintains a delicate, graceful presence with calm red hair, a slender frame, and reserved poise. Her speech is notably polite and formal, frequently using "watakushi" for self-reference. She embodies a ladylike aura from aristocratic upbringing, tempered by quiet introspection and a tendency to touch fingers to lips when thoughtful.

Academically exceptional, she honed extraordinary tactical planning skills, crafting complex strategies within seconds. Her espionage specialty is disguise mastery—precise replication of appearances, mannerisms, and voices, including male impersonation. This expertise stems directly from childhood efforts to hide her birthmark and navigate hostile environments.

Androphobia crippled her performance in training scenarios involving men, branding her a washout recruit. Her life pivoted upon meeting Klaus, leader of spy team Lamplight. He accidentally saw her unmasked face and uniquely called her birthmark beautiful. This acceptance ignited intense romantic feelings, making Klaus the sole man she comfortably engages with. She often interprets his actions romantically, proposing gestures like shared sleep or requesting hugs as mission rewards. Klaus remains romantically indifferent, viewing bonds through a familial lens; he gently redirects her affections while valuing her as chosen family.

Within Lamplight, she and Thea are the oldest members. Grete frequently seeks Thea’s romantic advice, viewing her as a love and charm mentor. She demonstrates fierce loyalty and protectiveness toward teammates, notably devising rapid plans and deploying trackers to rescue team leader Lily in a crisis. Her courage and strategic mind earn respect, even from stubborn peers. Junior member Sara actively admires her bravery, hoping Klaus notices. She also cares for Klaus, removing his pen to prevent overwork.

Operationally, she provides crucial support during infiltration or deception missions. An early assignment leveraged her disguise skills to counter a lethal assassin, underscoring her vital role despite personal challenges. Her emotional journey balances unrequited love with growing confidence through team contributions and Klaus’s platonic support. Her original codename, "Daughter Dearest" (Manamusume), reflects yearning for familial love denied at birth. Later, Klaus symbolically renames her "Ashes," acknowledging transformative growth and resilience beyond her past.

She enjoys making clothes and voices feelings through quotes—like desiring even "1%" of Klaus’s love if meeting expectations—while acknowledging improbable reciprocation. A core desire to be loved and valued drives her persistent efforts within Lamplight.