Chiyochichi is a bizarre and memorable figure from Azumanga Daioh, presented as a strange, yellow to orange-colored, cat-like creature. His name directly translates to Chiyo-Dad or Father Cat, which is the claim he makes about his identity. He is not a regular part of daily life, as he primarily appears to the characters Sakaki and Osaka within their dreams. His first appearance is in a New Year's dream experienced by Sakaki, where Chiyo introduces him as an abandoned cat that needs help. After Sakaki cares for him, he reveals his true nature as Chiyo's father and thanks her for looking after his daughter. It is during this encounter that he also cryptically advises Sakaki to find a real cat.

The creature has a very distinctive and easily agitated personality. He is quite easily angered, and when his temper flares, he shakes violently while changing colors. Notably, he always maintains the same unchanging facial expression; even when upset, his pupils only get slightly smaller, and his mouth is never shown as closed. He harbors a strong discomfort for the color red, which extends to a dislike of tomatoes. Despite this, he is fiercely insistent that Chiyo eat her tomatoes to maintain her health. He is also inconsistent about whether he truly is a cat. In one dream, he shows self-awareness that he is not a real cat, but when Sakaki mentions this to him later, he grows angry and appears to have no memory of such a conversation. Other whimsical and unverified characteristics are attributed to him, including being bullet-proof, a great baseball player, or even Santa Claus.

His role in the story is less about advancing a central plot and more about providing surreal, humorous moments and exploring the inner thoughts of other characters. He functions as a shared imagined figure, acting as a stand-in for the absent parents of the child prodigy Chiyo Mihama, whose real mother and father are never seen. His appearances create a bridge to the subconscious concerns of the characters who dream of him. For Sakaki, who loves cats but is inexplicably hated by them, Chiyochichi represents a strange, fatherly figure who encourages her to find a real cat, addressing her deepest longing. For Osaka, who is more whimsical and childlike, his appearances are even more absurd, such as when he suddenly begins speaking English in her dream because his daughter is going to America.

Chiyochichi has specific key relationships, primarily with Chiyo, Sakaki, and Osaka. He claims to be Chiyo's father and behaves in a parental manner, concerning himself with her diet and asking what is popular at her school. His interactions with Sakaki are often paternal and advisory, as he asks her to confess her problems, such as her height and her trouble with cats. With Osaka, his interactions are more nonsensical; in one dream, she offends him by saying he resembles a particular politician. His existence is further blurred by the presence of physical objects. Osaka gives Chiyo a stuffed animal that looks exactly like Chiyochichi for her birthday, and the class also makes hats shaped like his head for a cultural festival, much to his dream-version's displeasure that he was not consulted first.

There is no traditional character development for Chiyochichi, as his nature remains as enigmatic at the end of the series as it was at the beginning. He does not learn or change, but rather serves as a constant, bizarre touchstone. The notability of Chiyochichi lies entirely in his absurdity and the questions he raises. He is a creature of pure whimsy whose ambiguous existence is a hallmark of the series' surreal humor. He is neither confirmed nor denied to be Chiyo's real father, leaving his true nature as a shared dream, a collective unconscious symbol, or simply a very strange plushie come to life, open to interpretation. For reasons that remain unexplained, he also seems capable of levitation or floating in various random locations.