Kanako Tatsumi is the younger sister of Souichi and Tomoe Tatsumi, residing in Nagoya, Japan. She is fourteen years old with brown hair and brown eyes.

Kanako mistakenly believes her brother Souichi and Tetsuhiro Morinaga are in a romantic relationship, a belief that grows more accurate as their relationship develops. She is supportive of them and often teases Souichi about it, discussing their latest developments with Taichirou Isogai.

She possesses a lively personality typical of a teenager and is deeply engaged with anime and manga fandom. Kanako actively interacts with online communities, answering questions and sharing information about the series.

She expresses a romantic interest in Taichirou Isogai, believing they would make a good couple. Kanako is aware of Souichi's homophobia and violent temperament, and she deliberately avoids encountering intimate situations between him and Morinaga.

Her father is Soujin Tatsumi, a scientist who travels frequently and maintains an interest in bugs and nature. The family home is destroyed in an arson attack by a stalker targeting Souichi, an event which greatly impacts the family.

Throughout the series, Kanako remains a consistent and supportive sibling figure who provides comic relief through her interactions and misunderstandings.