Bertholdt Hoover attends Attack Junior High School as a first-year student, distinguished by his tall stature, shaggy dark hair, and consistent use of the standard male uniform. Though the tallest in his class, he feels overshadowed by his confident childhood friend Reiner Braun, fostering a quiet, reserved personality marked by social anxiety and self-doubt. He avoids attention, particularly around Annie Leonhart, toward whom he harbors an unspoken romantic interest. This causes frequent blushing, awkward conversation attempts, and difficulty expressing his feelings. Reiner and Ymir recognize his crush and occasionally intervene, often leading to comedic embarrassment.

Artistically skilled in die-cutting, a childhood hobby, Bertholdt once impressed a summer festival booth owner with his expertise, earning masks as a reward. In the present, he revisits the same booth where Annie finds him, recalling his past interest. They bond briefly over the activity, but Bertholdt invites her to join rather than confessing—frustrating Reiner and Ymir's hopes for romance.

His school activities span club events like the Scout Regiment, volleyball, and dodgeball tournaments. During one match, he sacrifices himself to block a ball targeting Annie, securing her team's advancement. He participates in athletic fairs, cultural festivals, and test-of-courage events, yet frequently faces humiliation—such as an off-key band performance that incapacitates listeners. When offering academic help to Sasha Blouse, she overlooks him, deepening his embarrassment.

Interactions with Annie feature missed opportunities: he showcases crunches-earned abs only for her to gut-punch him, and attempts animal sounds alone with her before fleeing when Reiner interrupts. Small connections emerge, like Annie acknowledging comfort around him during the festival. His foundational bond with Reiner involves mutual reliance; Reiner encourages his confidence while Bertholdt admires his assertiveness. Ymir alternates mocking and advising him, dubbing him "Mr. Stare-thol" for his obvious gazes at Annie.

Key moments include accidentally injuring teammates during sports day, prompting first-year apologies to upperclassmen. During a test of courage, he and Reiner encounter supernatural phenomena before crashing into the gym with a cannon. He later assists Eren Jaeger’s chee-burg stand at the school festival, defending it against interfering teachers.

While persistently avoiding attention, Bertholdt shows faint self-improvement—asking Annie to the festival or volunteering to swap tainted omelet rice with Reiner during a maid café incident. Despite setbacks, his loyalty to friends and quiet resilience remain constant.