Ernesta Kuhne is a student of Allekant Academy, one of the six schools in the city, and serves as the famous representative of the institution's Pygmalion faction, also known as the Sculpture faction. At the age of seventeen, she stands as a genius in the field of Meteorite Engineering, the study of the magical meteorites that power much of the world's advanced technology, and is a leading researcher in the development of autonomous puppets, or "Lux". Her appearance is marked by light chestnut hair tied up in a ponytail, sea green eyes, and a standard Allekant uniform typically worn under a lab coat, reflecting her constant engagement in research activities.

In terms of personality, Ernesta presents a contradiction. On the surface, she appears as a peppy, cheerful, and somewhat mischievous girl with a lighthearted and occasionally childish demeanor, such as when she teasingly denies having fallen asleep. However, this exterior masks a profoundly calculating and obsessive scientific mind. She has a dark sense of humor and enjoys toying with opponents and research subjects alike, sometimes giving them handicaps purely for her own amusement. Described as a "science maniac," she possesses a willingness to perform any experiment necessary to achieve her goals, embracing a philosophy of internal "ebullience". She finds excitement in taking risks, a trait that stands in stark contrast to her more cautious best friend and partner, Camilla Pareto.

Ernesta's core motivation is driven by a grand and idealistic dream for her creations. Her ultimate wish is for autonomous puppets to one day coexist with humans and be granted the same rights as living beings. This desire to create a truly "living" robot fuels all her actions and research. To realize this dream, she is shown to be highly pragmatic and willing to make calculating moves. During the events of the Phoenix Festa tournament, she deployed two of her advanced creations, the autonomous puppets AR-D and RM-C, to compete as proxies for herself and Camilla, ultimately earning the runner-up position. Following the tournament, she was approached by an antagonistic organization called the Golden Bough Alliance. Recognizing the potential to acquire rare and necessary materials for her third puppet, she eventually agreed to assist them, producing over a thousand mass-produced puppet units in exchange for the resources she needed, even though she had little interest in the alliance's broader ambitions.

Critical to her character is her relationship with Camilla Pareto, a fellow researcher and the head of the Lion faction. Camilla is not only her best friend but also the engineer who handles the hardware construction of their projects, complementing Ernesta's theoretical genius. It is even revealed that Ernesta saved Camilla's life using her puppet technology, deepening the bond between them. Beyond this partnership, she views other characters primarily as subjects of interest, seeing the protagonist Ayato Amagiri as a fascinating source of combat data for her research. She also treats her own puppet creations almost as if they were her children, particularly her third unit, Lenate, whom she dotes on like a daughter.

As a Genestellar, the new human race born after a world-changing catastrophe, Ernesta possesses enhanced physical capabilities and can manipulate an aura known as prana. However, her true combat power is not physical but intellectual. She boasts a genius-level intellect and a "steely calculation" ability, combined with an exceptional talent for creating and programming autonomous puppets. Her role in the story is that of a powerful supporter and occasional antagonist, a scientific prodigy whose immense technical abilities and morally flexible pursuit of her dream make her a significant force within the world, capable of shaping events from behind the scenes.