Chi is a small grey and white American Shorthair kitten with black stripes and large eyes. Separated from her mother and siblings during a walk, she is discovered alone by a young boy, Yohei Yamada, and his mother, Miwa Yamada. Though their apartment complex forbids pets, the family takes her in temporarily. Unable to find alternative arrangements, they ultimately decide to keep her.

Her name comes from an incident during housebreaking where she urinates indoors. Hearing the Japanese word for urine, "shikko," she mistakenly responds to the syllable "Chi," which becomes her permanent name. Initially disoriented in her new environment, she experiences fear towards unfamiliar elements like baths, large dogs, and visits to the veterinarian, often involving Yohei's father.

Chi's personality combines curiosity, stubbornness, and affection. She exhibits loud vocalizations, plays enthusiastically with small moving objects, and forms strong attachments to the Yamada family, though her vocal nature risks exposing their violation of the no-pets policy. Over time, she adapts to domestic routines, learns to use a litter box, and develops preferences for specific foods like sushi. Her explorations extend beyond the apartment, leading to encounters with other animals. She meets an older cat, Blackie, who assumes a quasi-maternal role, offering guidance and protection during outdoor adventures. She also forms friendships with fellow kittens, including Cocchi, sharing playful experiences.

Her development includes episodes of independence, such as briefly running away or engaging in outdoor escapades, but she consistently returns to the Yamadas, indicating a growing bond and sense of belonging. Challenges like illness, grooming sessions, and confrontations with larger animals contribute to her gradual increase in confidence, though residual fears of dogs persist. Her perspective on the world evolves through these experiences, balancing her innate playfulness with learned caution.