Hulmy is a skilled magic item engineer and the childhood friend of Lammis, a fellow survivor from the destruction of their home village by monsters. This tragic event, in which both lost their parents, forms the foundation of her deep bond with Lammis and shapes her strong, protective nature. Hulmy is a young woman of tall stature with long, unkempt brown hair, often seen wearing a black overcoat. Her physical appearance is said to fit the image of a tough engineer with a delinquent vibe.

Her personality is notably confident, outspoken, and brash, frequently using rough, delinquent-style language. She even uses the masculine pronoun "ore" when referring to herself, which highlights her bold and unconventional nature. Despite a lack of physical combat abilities, she possesses remarkable courage and a fearless attitude, allowing her to intimidate even dangerous foes. Hulmy has a curious and analytical mind, often displaying "mad scientist" tendencies as she pursues her research. Her actions as a child sometimes caused trouble due to her experiments, but she is deeply reliable and a loyal friend, especially to those she cares about.

Hulmy's primary motivation is her passion for understanding and creating magic items, driven by an insatiable curiosity. She joins the labyrinth exploration team as an investigator in order to apply her skills and aid her companions. Her role in the story is central to unraveling the mysteries of the world's magic technology and, most importantly, the nature of the protagonist, Boxxo the vending machine. She is the first character to correctly deduce that Boxxo houses a human soul, and she forms a unique partnership with him to escape dangerous situations and solve problems.

Her key relationships include her deep, sisterly bond with Lammis, whom she treats like a younger sister. With Boxxo, she is a close friend and intellectual collaborator. The narrative also suggests that she has romantic feelings for him, making her a potential love rival to Lammis. She also has a professional relationship with Suori, whom she supports by participating in magic tool exhibitions.

Throughout her development, Hulmy faces several life-threatening situations. At the outset of the story, she is kidnapped by a bandit group who force her to study Boxxo. Later, during a confrontation with the King of Souls, she is captured and put into cardiac arrest. She is revived through teamwork, with Boxxo using an AED function and Lammis performing chest compressions, a near-death experience that deepens her bond with the group. In the anime adaptation, an original scene shows her thanking Boxxo with a kiss after being revived. She also demonstrates her integrity at a magic tool exhibition when she quickly disables an illegal humanoid automaton that had a human soul forcibly implanted into it, halting its violent rampage.

Notable abilities include her exceptional skill as a magical tool technician. While she cannot fight physically, her real strength lies in her sharp intellect, outstanding analytical abilities, and a scientific approach to problems. She excels at conducting experiments, deciphering complex magical devices, and assessing magical technology rapidly. Her ingenuity and quick thinking are crucial for the survival and success of her companions, often allowing her to turn the tide in dire circumstances without the need for brute force.