Futaba Yoshinaga, the youngest in her family, is noted for her boyish demeanor and tendency to cause trouble. She initially resents the sentient gargoyle statue Gar-kun, won in a local lottery, whose protective behavior at their entrance draws unwanted attention and notoriety to her family. This antagonism defines her early interactions.

Her perspective gradually shifts as she witnesses Gar-kun's dedication to safeguarding her family and the wider Goshikichō community. This leads to acceptance, transforming her view of the gargoyle from a nuisance to a genuine protector and family member. Her friendships, including one with Mimori Onodera (whose father relies on a guide dog) and Lili Hamilton (a girl granted psychic abilities through alchemical experiments by her father), integrate her into the town's dynamics and conflicts.

Physically assertive, Futaba frequently employs wrestling techniques like German suplexes, a trait shared with other female Yoshinagas. This combative nature starts as aggression but evolves into defending those she cares about. Her capabilities expand through alchemy, using a specialized helmet created by Iyo Takahara to communicate with plants. This ability occasionally aids in resolving community challenges, such as assisting local merchants facing threats.

Her family environment shapes her behavior. Interactions with her older brother Kazumi, whose reserved and effeminate nature contrasts with her assertiveness, often involve him mitigating her impulsive actions, highlighting a sibling dynamic of friction and underlying loyalty. Her largely silent mother displays similar physical ferocity when provoked, reinforcing this familial pattern of protective aggression.