Eld Gin attends Attack Junior High School as a second-year student and belongs to the unauthorized Attack Junior High Scout Regiment club. He acts as the steady anchor within the club, consistently offering calm judgment during their activities. His grounded personality balances the more eccentric members, providing a reliable voice of reason.

He possesses neatly tied-back blond hair and golden eyes, often seen wearing a blue hoodie under his standard school uniform. Eld shares a close bond with Gunther Schultz, frequently appearing together during school and club events.

Demonstrating concern for peers, he rushed to Oluo Bozado's side when Oluo collapsed from biting his tongue. Initially suspecting an attack, Eld expressed shock at what seemed an inhuman act, though his concern eased once the actual cause was known. He actively participates in school life, including scolding first-year students like Jean Kirstein about their behavior and appearance alongside classmates, leading to assigned cleaning duties as collective punishment.

He competes in Sports Day, carrying Petra Ral with Oluo and Gunther during the shoulder wars, and later assists underclassmen with court cleanup. For the Scout Regiment club's "Test of Courage" aimed at new members, he and Gunther dressed as Titan models, hiding in the science room to surprise first-years before revealing themselves after a gym chase.

During the 104th festival, he waits in line with classmates for cheeseburgers at the first-years' food stand. When Gunther mentions a cute salesperson, both react with visible surprise and blush when Armin Arlert arrives in an unexpected outfit with their order. Later, he watches Ilse Langnar's broadcast of Eren Yeager venturing into the principal's office, showing relief when Eren successfully retrieves a cheeseburger.