Jiji is the black cat companion of Kiki, the young protagonist. He is the same age as his owner, thirteen years old, and has been with her since infancy, making their bond deep and long-standing. As a familiar, Jiji is not an ordinary pet; he possesses the ability to speak and converse directly with Kiki. This communication is a result of their close relationship and Kiki’s magical nature, though other humans cannot understand him, hearing only typical cat meows.

In terms of personality, Jiji is clever, expressive, and often serves as a grounding, pragmatic counterpart to Kiki. He has a sharp tongue and a sarcastic wit, frequently offering cheeky or grumpy commentary on the situations they find themselves in. Despite his occasional complaints when things become difficult, his loyalty to Kiki is unwavering, and he is consistently protective of her. He acts as her primary confidant and sounding board, the only one with whom she can openly discuss her doubts and fears as she navigates a new life in a unfamiliar city.

Jiji’s role in the story is multifaceted. He is Kiki’s closest friend and a constant source of emotional support, helping her to adjust to the bustling seaside town of Koriko. He is an active participant in her delivery service, sometimes getting roped into tricky situations, such as when he is forced to pose as a stuffed toy to complete a delivery. His presence also provides much of the film’s humor, balancing Kiki’s earnest and sometimes stubborn nature with his own more cynical and realistic observations.

A key relationship in Jiji’s personal arc is with Lily, a sophisticated white female cat belonging to a customer of the bakery where Kiki lives. Initially nervous around her cool and aloof demeanor, Jiji becomes smitten and begins spending more of his time with her. This new relationship draws him away from Kiki and is a significant part of his individual development, paralleling Kiki’s own journey toward forging new connections.

The most significant change for Jiji is the loss of his ability to speak with Kiki in the latter half of the story. After Kiki loses and then regains her flying power, Jiji no longer speaks to her. This is not presented as a loss of magic, but as a symbolic representation of Kiki's emotional maturation and growing independence. Jiji's talking nature is understood as an external manifestation of Kiki’s own self-doubt and the internal conversations she has with herself. As she becomes more confident, makes human friends, and finds her place in the world, she no longer needs that external voice in the same way. While they remain close friends, cuddling and interacting at the end of the film, their relationship has transformed, signifying that Kiki has learned to stand on her own. By the story's conclusion, Jiji has started a family with Lily, having three white kittens and one black kitten, illustrating his own path towards an independent life beyond being solely Kiki’s companion.