Iina Chiyo, universally recognized only as Class Rep, holds the position of class president at Isono Junior High. She possesses green hair and brown eyes, consistently wears glasses, and is always seen in her school uniform complete with a neckerchief and tie. Her well-endowed figure surprises classmate Mawari Zenigata and sparks jealousy. Removing her glasses reveals a strikingly beautiful appearance that causes Nagasumi Michishio to blush. Despite her role, she maintains a passive presence, often overlooked by classmates who remain unaware of her real name for most of the series.

A profound desire for others to know her real name drives her character. This core motivation culminates in the manga's final volume when Mawari Zenigata finally reveals her name, Iina Chiyo, prompting her triumphant victory cry.

A pivotal moment occurs when she writes a love letter confessing strong feelings for Nagasumi, but mistakenly addresses it to Sun Seto due to not looking directly at the recipient. This error triggers the emergence of her alternate persona, the "Last Amazoness" – a confident, girl-loving warrior identity she adopts to gain attention or courage. This persona actively declares romantic intentions towards Sun.

Later, she receives the mermaid weapon "Gender-X" from Surtan, which physically transforms her when she assumes the Last Amazoness identity. Using this weapon, she engages in combat against troublemakers, shifting from her reserved demeanor to a proactive role. She occasionally collaborates in these efforts with Maki, a member of the Seto Group, whom she misidentifies as a fairy.