Hyulmi is a talented maker of magical items and the childhood friend of the huntress Lammis. Her past is marked by tragedy, as her hometown was destroyed by monsters, an event in which she lost her parents and from which only she and Lammis are said to have survived. This shared trauma forms a deep, unspoken bond between the two women, who see each other as found family.

In terms of personality, Hyulmi is best described as bold, brash, and fiercely confident. She has a tall stature and a commanding presence, often speaking in a rough, delinquent-like tone and referring to herself with masculine pronouns. Despite lacking any direct combat abilities, her courage is immense; she has been known to intimidate her own captors while being held prisoner. She possesses a sharp, analytical mind and a deep curiosity, especially regarding anything mechanical or magical. This curiosity sometimes veers into "mad scientist" territory, and she admits that her youthful experiments often caused more trouble than good for those around her.

Hyulmi's primary motivation is her passion for research and understanding complex mechanisms. This drive to analyze and create is the core of her identity as a magic-item engineer. However, her actions are also strongly motivated by loyalty, particularly to her friends. She is not driven by personal glory in combat but by the desire to support her companions with her intellect and technical skills.

In the story, Hyulmi serves a critical role as a technical specialist and strategist. She is first introduced in a captive situation, having been kidnapped by a bandit group who forces her to study a strange vending machine named Boxxo in an effort to extract its wealth. During her imprisonment, she becomes the first character to deduce that Boxxo houses the soul of a human from another world. After being rescued by Lammis and the others, she becomes an invaluable member of their labyrinth exploration team. While she does not fight on the front lines, her ability to analyze enemy magical devices, solve mechanical puzzles, and maintain equipment is essential for the party's survival and progress.

Her key relationships are with Boxxo and Lammis. With Lammis, she shares a history of survival and acts as a protective, older-sister figure. With Boxxo, she forms a unique partnership; he provides the mysterious mechanisms and support items, while she provides the understanding and analysis of his nature. She demonstrates a clear romantic interest in Boxxo, which becomes a subtle point of connection and potential rivalry with Lammis. She is also a close ally to other party members like Suori.

Hyulmi undergoes notable development as she moves from being a solo researcher causing chaos with her experiments to a key member of a reliable team. A significant moment in her journey occurs during a confrontation with the Netherlord, where she is fatally wounded and suffers cardiac arrest. She is revived through the combined efforts of Boxxo, who uses a defibrillator function, and Lammis, who performs chest compressions. This near-death experience and her subsequent recovery solidify her role as a cherished member of the group. In one adaptation of the story, this event is followed by a moment where she expresses her deep gratitude by kissing Boxxo.

Her notable abilities lie entirely in her intellect and technical expertise. As a master magical tool engineer, she can rapidly analyze the structure and function of complex magical devices. Her investigative skills are so sharp that she quickly pierced the secret of Boxxo's true nature. She also proved capable of deactivating a rampaging, illegal magical item by analyzing its core and releasing the human soul trapped within. While she has no physical strength for battle, her cleverness and problem-solving skills make her one of the most capable members of the party in non-combat situations.