Scarlett Cypher, alias Carlie, operates as a Yggdrasil Group professional with a history as a subspace diver. She served alongside Professor Mugen and his team during diving expeditions, though her early life remains obscure. Her appearance features long blonde hair in a bun with trailing strands and face-framing curls, blue eyes, and red lipstick. She typically wears a black sleeveless dress with red accents, including a sheer upper section, gold bracelets, tights, and red high-heels, occasionally layered with a red buttoned coat. At Hrbek Oda, she dons a jagged red spacesuit with a triangular helmet. In youth, she wore a black sleeveless dress with a red collar, large brown belt, and goggles, her hair shorter. Glowing red patterns once manifested on her skin and suit during a dive; their source—implants, the Flawen submersible, or the suit—is unverified.

Her demeanor presents seriousness and professionalism, underscored by an enigmatic, slightly aloof aura focused on objectives. In *Abyss of Hyperspace*, Yggdrasil recruits her to secure Professor Mugen’s legacy, specifically the Advaseele submersible. She accepts without full knowledge of Yggdrasil’s goals, driven by personal curiosity about the professor’s unfinished pursuits. She oversees the Bentenmaru’s pursuit, confronts Marika Kato’s crew in New Okuhama City under a non-aggression pact, and leads a boarding action on Mugen’s ship at comet Hrbek Oda. There, she engages Ririka Kato in unarmed combat, retreating due to structural damage.

Her capabilities include piloting subspace submersibles like the Flawen and proficiency in hand-to-hand combat. Professor Mugen’s dialogue implies her technical expertise in submersible construction. Her relationship with Mugen centers on their shared diving history, undefined in depth. Interactions with his son Kanata lack overt hostility despite her antagonistic role. During a subspace chase after the Advaseele, she urges Kanata to surrender, citing his resentment toward his father’s diving obsession. After his refusal, she pursues him deeper into subspace until forced to surface by her craft’s emergency systems. Retreating, she acknowledges a likeness between them, murmuring they are "the same."

Per the *Abyss of Hyperspace Drama CD*, Kanata later assisted in subspace salvaging with a colleague of his father, and a subsequent letter from him originated from her residence.