Chiho Mihara is one of the twin daughters of Chitose Mihara, the kind-hearted owner of the apartment building where the protagonist, Hanato Kobato, resides. She is the younger of the two sisters, with her twin, Chise, being the elder. Chiho and her sister are recognizable by the colors of their headbands and clothing, which are used to tell them apart. They are both around the age of eleven or twelve and live a normal, happy life with their parents.

Chiho and Chise share a connection to CLAMP's earlier work, Chobits, as their physical appearance strongly resembles the characters Chii and Freya from that series. Unlike those characters, Chiho and Chise are depicted as ordinary human girls with no connection to computers, and they express a full range of emotions. For fans familiar with the tragic fate of the characters in Chobits, seeing Chiho and Chise living peacefully with their family serves as a heartwarming contrast.

Within the story of Kobato, Chiho primarily serves as a member of the Mihara household, providing a warm and supportive environment for Kobato. Through the consideration of Sayaka Okiura, a nursery school teacher and friend of Chitose, Kobato comes to live in the apartment managed by Chitose, where she interacts with Chiho, Chise, and their mother. Their home acts as a stable and comforting base for Kobato as she undertakes her mission. Chiho's notable interaction with Kobato involves helping her find a new owner for an abandoned kitten. She initially worries about the cat's welfare but later experiences emotional healing after listening to Kobato sing, demonstrating her caring nature and her role as someone whose heart can be touched by Kobato's actions. No information is available about Chiho having any special abilities, personal motivations of her own, or significant character development throughout the series; her role is consistently that of a supporting character who contributes to the series' atmosphere of kindness and nostalgia.