Maeter is one of three young children adopted by Eureka, and later Renton Thurston, during the events of the series. Her exact origins are tied to a tragic incident in the past; she and her brothers, Maurice and Linck, were orphaned during a mission carried out by Eureka and Holland when they were still part of the military. Eureka, upon realizing the consequences of her actions, took the children in to care for them. At the start of the main story, Maeter is approximately four years old.

In terms of personality, Maeter is characterized as an outspoken and spoiled young girl. She is known for her teasing nature and for throwing temper tantrums. Despite her young age, she possesses a strong-willed and somewhat mischievous demeanor, often using her behavior to get what she wants or to express her displeasure. A central aspect of her personality is her deep-seated fear of abandonment. This manifests as a fierce protectiveness over her adoptive mother, Eureka, stemming from a constant worry that Eureka will one day leave her and her brothers behind.

This fear largely defines her initial motivations within the story, particularly concerning Renton Thurston. When Renton joins the Gekkostate and begins to develop a close relationship with Eureka, Maeter feels threatened. She, along with her brothers, perceives Renton as an outsider who intends to take their beloved mother away from them. As a result, Maeter and her siblings subject Renton to a series of pranks and general hostility in an attempt to drive him away. Her role in the narrative is primarily as part of the surrogate family unit at the heart of the Gekkostate's ship, the Gekko. She serves as an obstacle for Renton to overcome in his quest for Eureka's affection and also as a catalyst for Eureka's development as a parent, forcing her to confront human emotions like discipline and care.

Maeter’s key relationships are almost entirely familial. Her most significant bond is with Eureka, whom she loves unconditionally and sees as her true mother. She is very protective of this bond, which is why she initially rejects Renton. Her relationship with Renton evolves slowly over the course of the series. While she is the first of the three children to begin warming up to him, acknowledging his achievements and spending time with him as early as the second season, she continues to tease him and call him names until near the end of the series. By the conclusion, she fully accepts him as her adoptive father. She also shares a close sibling bond with Maurice, her older brother, and Linck, her younger brother. She often cares for them and is protective of them, just as they are protective of her.

Throughout the story, Maeter undergoes a notable development from a hostile, mistrustful child into an accepting member of a new family. Her arc is one of learning to trust and overcoming her fear of loss. While she is too young to fully remember her biological mother, a poignant moment late in the series suggests she retains a faint, sensory memory of her, implying a deep-seated longing for maternal love that she ultimately finds in Eureka. In a separate novel continuity that reinterprets the story, Maeter appears as the only adopted child, being a newborn rather than a four-year-old. Maeter does not possess any combat or piloting abilities. Her notable traits are her strong emotional instincts and her behavior as a young child, including being unable to read despite receiving advanced homework from Eureka.