Chonbo is a mahjong spirit inhabiting a formerly abandoned mahjong parlor once run by Nashiko Jippensha's father. Its physical form resembles a small sparrow chick, featuring distinctive tail feathers modeled after the peacock imagery found on the one-bamboo mahjong tile from which it emerged. Izumi Tokutomi spontaneously named it "Chonbo," referencing a severe mahjong penalty for unfair rule violations. Chonbo is aware of this negative connotation and expresses displeasure, but the name remains in use; another character notes it is unlucky.

Communication with humans is possible only with Nashiko Jippensha, who can hear and understand it. To all others, Chonbo appears and behaves as an ordinary sparrow, maintaining this facade. As a mahjong spirit, it possesses refined skills and high intelligence. Before Riche Hayashi joined the group, it served as the fourth player in mahjong games with Nashiko and her friends due to the lack of human players.

Chonbo spends its days freely roaming the mahjong parlor, observing and participating in activities. Despite its spiritual nature and contributions, Nashiko often treats it roughly, including documented instances of near use as food and abandonment at the parlor during group training camps. Its presence contributes to the parlor’s operations and the group’s dynamics through mahjong gameplay and occasional indirect interactions with the environment.