Kobayashi is the central human figure around whom the narrative focuses. She is a twenty-five-year-old systems engineer leading a solitary, routine existence until a drunken encounter in the mountains dramatically alters her life. During this incident, she impulsively removes a holy sword from the dragon Tohru, and a hazy promise made in that moment leads to the dragon becoming her live-in maid. Her ordinary apartment then becomes the setting for an extraordinary household.

Her personality is defined by a deep-seated stoicism and a pragmatic, level-headed nature. She rarely displays strong emotions outwardly and consistently acts as the voice of reason against the whims of the magical beings who enter her life. Despite this cool exterior, she demonstrates genuine kindness and reliability, consistently putting the needs of her growing family first. She possesses a dry, deadpan sense of humor. A notable contradiction to her usual composure is her behavior when intoxicated, which transforms her into a boisterous and overly honest version of herself. She also harbors a specific, quietly indulged fascination with maid culture.

Kobayashi's motivations are initially driven by a sense of obligation and guilt, pushing her to honor a promise made while drunk. This foundation evolves into a sincere desire to protect and provide a stable, harmonious home for Tohru, the exiled dragon child Kanna, and the others who later arrive. She acts as a guardian, helping the dragons navigate and adapt to human society while maintaining a sense of normalcy.

Her role in the story is that of the protagonist and emotional anchor. She provides the human perspective through which the audience experiences the chaos of the supernatural world. Her home functions as a central sanctuary, and she frequently acts as a mediator, problem-solver, and eventually the de facto matriarch of a family that bridges two worlds.

Key relationships define her journey. Her bond with Tohru is the emotional core of the series, beginning as a transactional arrangement of master and servant before deepening into a partnership based on mutual trust and genuine affection. With Kanna, Kobayashi assumes a parental role, learning to offer emotional support and patience. At work, her friendship with the equally pragmatic Makoto Takiya provides a grounding human connection. Her interactions with other dragons such as Elma, Lucoa, and Fafnir continuously challenge her patience and broaden her understanding of family and loyalty.

Throughout the series, Kobayashi undergoes a quiet but significant transformation. She transitions from a solitary individual focused entirely on work to someone who actively embraces and prioritizes family life. She learns to openly express her care for others and becomes far more emotionally available, adapting to the chaotic love of her dragon family.

As a thoroughly normal human, Kobayashi possesses no magical or supernatural abilities. Her strengths lie in her sharp intellect, particularly her skills as a programmer, and an extraordinary tolerance for alcohol. Her most defining capabilities, however, are her boundless patience, pragmatic problem-solving skills, and an unshakable composure that allows her to negotiate with powerful mythical beings through calm logic and kindness rather than force.