Gamo-chan is a core member of Hayase Nagatoro's friend group, consistently present during group activities and school life. She sports orange hair and a tough appearance but reveals a mature, protective nature within her circle, often acting as an older sister figure to Nagatoro, Yoshi, and Sakura despite being their peer. Her family's ownership of a mixed martial arts gym underscores her connection to combat sports.

She initially joins the teasing of the introverted art club member known as Senpai, frequently using the nickname "Paisen." This specific moniker and her teasing occasionally spark jealousy in Nagatoro, who demands she stop. As the series progresses, Gamo-chan sharply observes the developing romantic feelings between Nagatoro and Senpai. She transitions from light torment to actively supporting their relationship, scheming with Yoshi and Sakura to bring them closer.

Supplementary material from manga Volume 10 identifies her English name as Maki Gamou, with her surname originating from Gamō Station.

Throughout the depicted second school year, she remains a fixture in Nagatoro's core group. She attends significant events, including Nagatoro's judo tournament and Senpai's academic challenges, maintaining her supportive role as Nagatoro and Senpai navigate their evolving relationship.