Tsurugi Kanegafuchi is a third-year high school student and chairwoman of her school's disciplinary committee. Her strict rule enforcement and imposing presence earn her the moniker "Iron Girl." She exhibits perfectionist tendencies and maintains a coolly authoritative demeanor, often appearing unapproachable. Despite this stern exterior, she harbors a secret interest in first-year student Ume Toranomon, remaining too prideful to openly acknowledge these feelings.

Tsurugi often masks her emotions by teasing those she likes, adopting a sadistic demeanor. In reality, she possesses masochistic traits and struggles against a longing for cute things, deeming them unsuitable for her persona. This internal conflict emerges in a dream sequence involving school teacher Kaori Asakusa, whose flirtatious remarks about Tsurugi's physical appearance and emotional isolation provoke visible distress. Tsurugi is later discovered crying in her sleep, dismissing it as weakness if confronted.

One notable incident sees her inspecting Yuri Asakusa's uniform violations. Under the pretext of measuring skirt length, Tsurugi inappropriately measures Yuri's bust size, prompting accusations of sexual harassment. She deflects accusations through disciplinary justifications, showcasing how she wields authority to sidestep vulnerability. Her interactions with Ume feature Tsurugi veiling concern behind criticism, highlighting her struggle to express genuine affection.