Marlya Noel hails from Suna, a village annihilated in the War of Unification by Ray Dawn's forces. She and her childhood friend Veronica Thorn were the massacre's sole survivors. This tragedy, coupled with the deaths of her parents shortly after her birth and her subsequent guardian, etched deep emotional scars and cemented her belief in being a "cursed child." Villagers in Suna shunned her for this perceived misfortune. After Suna's destruction, she parted ways with Veronica and joined the Biaklay mafia family. Working in security, she leveraged their resources to track Veronica, drawing on wilderness tracking, hunting rifle, and blade skills honed by her hunter guardian.

Her path shifted at a black market auction where she encountered Free Underbar. Chaos erupted when Veronica attacked to steal a page of the Black Fairy Tome. During the upheaval, a freed fairy primordial—later known as Ash Clad—merged violently with Marlya without the standard organ transplant, making her a unique case of direct fairy possession previously deemed impossible. The fusion triggered flashbacks of Suna's destruction and Veronica's vow of revenge. Awakening, Marlya manifested Ash Clad to intervene in Free and Veronica's fight, enabling Veronica's escape. Facing arrest for illegal fairy use, Marlya accepted Free's offer to join the government agency Dorothea, viewing it as a path to pursue Veronica while containing fairy threats.

Within Dorothea, Marlya primarily operated alongside Free Underbar. Her fairy, Ash Clad, grants superhuman physical traits, flight, low-mid level regeneration, and fire manipulation. It generates extreme heat from its arms, reducing anything it touches to ashes. In combat, she employs a sniper rifle for ranged attacks (Street level destructive capacity) and Ash Clad for close-quarters engagements (Wall level destructive capacity). However, she retains average human speed, strength, and durability; any damage inflicted on Ash Clad physically harms her. Early missions saw Ash Clad's abilities strain her severely, causing unconsciousness after overuse.

Marlya's character arc centered on her obsession with Veronica, leading to repeated confrontations during her Dorothea service. Initial encounters saw Veronica dismiss or warn her away, most notably after a skirmish with Jonathan Passpierre where Marlya forced Ash Clad's manifestation to escape. This fixation fueled self-blame, intensifying after comrade Oz Mare sacrificed himself protecting her from Beevee Liscar's train ambush. His death reinforced her "cursed child" belief, nearly driving her to abandon Dorothea. Free Underbar's mentorship helped her process this guilt, emphasizing camaraderie and purpose beyond Veronica. She gradually evolved from emotional volatility towards resilience, channeling efforts into Dorothea missions like guarding Ray Dawn or securing fairy weapons and tomes. Her final confrontation with Veronica occurred during a ruined castle mission where they fought Wolfran Row together. Accepting Veronica's subsequent departure symbolized Marlya's emotional resolution and solidified her commitment to Dorothea.

Marlya possesses auburn hair and green eyes, typically clad in the standard Dorothea uniform with a sniper rifle on her back. Initially depicted as emotionally vulnerable and singularly focused on Veronica, tear-streaked confrontations were common. Her self-perception as a bearer of misfortune stems from past losses. Yet, she demonstrates tenacity in pursuing goals, wilderness survival skills, and tactical tracking abilities—like identifying backtracking patterns in footprints. Relationships within Dorothea, particularly with Free and Klara Kysenaria, provided stability, aiding her transition from a recruit needing guidance to a more assured agent.