Junko Mochida is a student council member at the Academy, managing budget allocations for school clubs like sports and literature. She openly maintains a lesbian relationship with fellow council member Nami Kozono, displaying their intimacy on school grounds with a submissive dynamic, addressing Kozono as "onee-sama." Junko possesses long turquoise hair secured by a black hairband, dark blue eyes, and large round glasses. She wears the Academy uniform with pink lingerie featuring dark pink bows.

Initially arrogant and self-righteous, she rejects a witchcraft club proposal from Hiroko Takashiro, Rie Morita, and Saki Shindou, scoffing at their idea. In retaliation, the trio casts a spell from a magic book designed to force a woman to "dance naked" and evoke pity. During a school assembly, while delivering budget announcements, Junko succumbs to uncontrollable sexual arousal. Compelled by magic, she strips her uniform and engages in vigorous public masturbation before the stunned students and faculty, losing consciousness after orgasm. She is moved to the infirmary to recover.

Post-incident, peers vilify Junko as mentally unstable, driving her into deep depression. She attempts suicide by stepping in front of a car but survives with help from classmate Reika Kitami. Her despair deepens upon discovering Kozono’s new relationship with unpopular male student Hiratani—also magically influenced. Junko’s personality shifts from confident to despondent and withdrawn. Her exclusively depicted sexuality through the Kozono relationship positions her among the narrative’s few lesbian characters. These events catalyze the witchcraft club’s formation and contribute to supernatural occurrences at the Academy.