Pi-chan, the younger sister of high school student Fuuta, moves into his residence at the series start, arriving with her cat, Kyuruga, as she transfers to a new school. Kyuruga initially resists her affection, biting when she tries to hold him. Pi-chan persists in engaging with the cat, showing him steady affection and taking primary responsibility for his care, including scheduling and attending veterinary appointments. Her daily routine involves feeding Kyuruga, playing with him, and observing his behaviors.

Over time, Kyuruga becomes more receptive. He begins begging Pi-chan for food and voluntarily seeks out her company. When Fuuta takes a trip, Kyuruga chooses to sleep in Pi-chan's bed, marking a deepened bond. Their dynamic shifts from initial friction to mutual comfort and closeness.

Pi-chan facilitates Kyuruga's integration into the household. She participates in naming him after observing a distinctive QR code-like pattern on his head fur during a photo attempt. Her enthusiasm for interacting with Kyuruga remains constant.

The series depicts routine moments between them, such as Kyuruga begging for chicken during meal prep or quiet companionship. While Pi-chan's social circle grows to include school friends, and she coexists with Fuuta's acquaintances like Miyama-senpai and his cats, her core narrative function centers on her evolving relationship with Kyuruga.