Kanna Kamui is a young dragon from another world who becomes a central figure in the human realm after being exiled. In dragon years, she is considered a child, with a mental and physical form resembling a human elementary school girl of about eight or nine years old, despite having lived for many centuries. She has white-lavender hair styled into two pigtails adorned with dark beads and large, expressive blue eyes. Her typical outfit is a distinctive white capelet with a fur collar, a pink blouse, a white frilly skirt, and pink shoes, a style once described as gothic lolita with a tribal theme. In her true form, she is a feathered dragon of significant size.

Her background is rooted in mischief and a deep-seated loneliness. For her excessive pranks, which were ultimately a misguided attempt to gain attention from her neglectful parents, Kanna was temporarily banished from the dragon world. She travels to the human world seeking Tohru, a fellow dragon she greatly respects and wishes to bring back home. Upon arriving, she initially distrusts the human woman Kobayashi, suspecting her of using magic to seduce Tohru away. However, when it becomes clear that she cannot return to her own world, Kobayashi offers her a place to stay. This act of kindness marks the beginning of a profound change in Kanna's life.

In terms of personality, Kanna presents a fascinating dichotomy. On the surface, she is often soft-spoken and stoic, rarely changing her facial expression or raising her voice. This quiet exterior, however, belies a deeply emotional and sometimes mischievous nature. She is incredibly curious about the human world, constantly asking questions about things like cars, playgrounds, and traffic lights. She is also a creature of strong appetites, possessing a ravenous hunger that leads her to happily snack on insects, crabs, fish, and other small animals she can fit in her mouth. Despite her physical smallness, as a dragon, her body is extraordinarily dense and heavy, a fact that often surprises humans who interact with her physically. While her tendency to play pranks lessens as she settles into her new life, she is not above using her cuteness or feigned sadness to get what she wants on occasion.

Her motivations evolve dramatically over the course of the story. Initially driven by a desire to return Tohru to their world and then a simple need for shelter, she soon finds herself wanting something she never had in her own home: a loving family. Her role in the story becomes that of a surrogate child to Kobayashi and a younger sister to Tohru, as she fully integrates into their unconventional household. She even adopts the human surname, calling herself Kanna Kobayashi. Beyond her home life, she also yearns to experience a normal human childhood. At Tohru's urging, Kobayashi enrolls her in a local elementary school, where she becomes a diligent if unusual student. Her role there is to learn about human society, make friends, and enjoy the simple, joyful experiences of childhood, like participating in sports festivals and going to the beach.

Kanna's key relationships define her development. Her bond with Kobayashi is central; she grows from being distrustful to deeply attached, openly clinging to Kobayashi, holding her hand, and seeking her constant attention, clearly seeing the human as a mother figure. Tohru acts as an older sister, taking responsibility for teaching Kanna about modern life, cooking for her, and acting as a bridge between her dragon nature and human society. At school, she forms a significant friendship with her classmate Riko Saikawa. Riko quickly becomes obsessed with Kanna, and the feeling is mutual. Kanna has expressed a desire for a future relationship with Riko similar to the one Kobayashi and Tohru share, hinting at a deep and potentially romantic affection for her human friend. Her development is also marked by a reunion with her biological father. In a significant event, Kobayashi helps Kanna confront her father, leading to an emotional reconciliation where Kanna openly cries in his embrace, finally resolving the feelings of abandonment that drove her early behavior.

As a dragon, Kanna possesses formidable abilities, though they differ from Tohru's. Her primary element is electricity. She can generate, manipulate, and even transform into electricity, allowing for powerful attacks and high-speed flight. A unique and iconic trait is her need to recharge her magical energy, which she does by inserting her tail into a standard electrical outlet, much like plugging in an electronic device. Without regular charging, her power weakens considerably. When sufficiently charged, her power is immense, classified as being at least mountain or even island level, and she has demonstrated the ability to fly from Japan to New York City in a very short time. Kanna also has the ability to learn human languages with astounding speed, picking up English fluently in just a few days while visiting New York. Despite these incredible powers, she has clear limitations; she is still a child, both emotionally and in her magical prowess, lacking the sophistication of Tohru's more advanced spells.