Izumiko Todayama serves as the personal maid to Itsuki Noya, the male heir of the Noya Group, and is the younger sister of Kyoko Todayama, president of Ebisugawa High School's Astronomical Club. Discovering Itsuki crossdressing to comply with Kyoko's all-girl club membership rule shocks Izumiko, prompting her to transfer schools and join the club to maintain proximity to Itsuki and assert her claim over him.

She frequently insists on being addressed as "Elizabeth Margaret." Izumiko treats Itsuki as a possession or toy, directing his actions and refining his crossdressing appearance, though underlying genuine feelings for him persist. Her dynamic with Kyoko involves rivalry and conflict over control of Itsuki, leading to competitive confrontations like a quiz battle interrupted by the student council president.

During the OVA's meta-fictional journey exploring their anime's production, Izumiko accompanies Kyoko to confront voice actors and visit the manga's editorial office, ultimately choosing integration into the manga world to preserve their existence. In this arc, she expresses insecurity about her breast size and undergoes a misguided "beauty treatment" from club advisor Shoko Omori. This includes inappropriate massages and practicing confessions to Itsuki while nude, an act Itsuki accidentally witnesses.

Izumiko exhibits moments of insecurity, particularly about her body, and displays naivety in social situations, such as unquestioningly following Omori's advice. Her loyalty to Itsuki remains consistent, driving her actions across all media. The series depicts no significant evolution in her core traits, with her role contributing to comedic and fanservice-oriented scenarios, including the club's parody-heavy escapades.