Caldina Kizaki, a third-year student in class 3-D, commands the "Gals" as their influential leader, her authority rooted in a fiercely competitive streak and a rivalry with Konome Kiritani that has simmered since elementary school. This enduring clash spans academics, personal challenges, and unyielding determination, with Caldina dismissing all contenders except Konome as unworthy adversaries.

When approached to join the "Hamedori Graduation Album," she scoffs at Tsukamu’s initial overtures, declaring only Konome a legitimate rival. Confident in her tactics—including covert maneuvers to tilt the odds—she challenges Tsukamu to a duel under terms she deems unbeatable. Yet her unexpected defeat forces her to grudgingly uphold their agreement. Post-loss interactions with Tsukamu diverge from her history with peers, gradually softening her stance and sparking an unanticipated willingness to collaborate beyond their bargain.

Caldina’s sway over the Gals renders her participation pivotal, as securing her cooperation is key to mobilizing the group. Her striking light blonde hair and piercing blue eyes mirror her assertive demeanor, while her senior status underscores her role as a seasoned leader, though her exact age remains unstated.