Hiyoko Tamaizumi is a third-year student at Misora Academy, serving as class president. She stands 161 cm tall with brown shoulder-length hair, brown eyes, and frequently wears glasses. Her physical measurements are 88-60-89 cm.

Financially supporting herself, she works part-time as waitstaff at the restaurant Alexander. Her primary ambition is to become a successful novelist, often writing under the pseudonyms "Hosokawa Tamaki" and "Tama Izumi". Her personality blends diligence and seriousness with classic tsundere traits; she initially displays a stern, no-nonsense attitude, particularly toward her coworker Shūsuke Chitose, whom she dislikes.

Her story forms one of the central narrative threads through its intertwining with Shūsuke's. Despite their rocky start, their relationship evolves as they collaborate at Alexander. Shūsuke supports her writing career, gradually fostering mutual respect and deeper emotional involvement. This dynamic drives her character development, showcasing a transition from rigidity toward a more open and collaborative demeanor.

Across all official media, including the visual novel prequel *Ore-tachi ni Tsubasa wa Nai ~Prelude~*, the main game, and the fandisc *AfterStory*, her role remains consistent: a dedicated writer balancing academic responsibilities, part-time work, and creative pursuits. Her interactions emphasize her growth in navigating professional challenges and interpersonal relationships, particularly with Shūsuke.