Bertholdt Hoover stands out as the tallest first-year student at Attack Junior High School, with shaggy dark hair and dark brown eyes, typically clad in the standard male school uniform. His imposing height contrasts sharply with his shy and socially withdrawn nature, often leaving him fading into the background. He lacks self-confidence and frequently feels overshadowed by his more assertive friend, Reiner Braun. Bertholdt deeply admires Reiner's outgoing personality and often seeks his advice to overcome his own timidity.

Secretly, Bertholdt harbors a significant crush on Annie Leonhart. This infatuation manifests through dreamy stares, visible blushing, and nervousness whenever she is near. His feelings are easily noticed by peers like Reiner and Ymir, who sometimes engineer situations to push him forward. Despite his social anxiety, Bertholdt possesses artistic talent, particularly in die-cutting, a skill he showcased with meticulous precision and creativity during the summer festival.

Bertholdt participates actively in school life. He sacrificed himself in a dodgeball tournament to block a ball aimed at Annie, revealing protective instincts toward her. Athletic events, like the Sports Day shoulder-war challenge, saw him inadvertently causing chaos by sending opponents flying. Academically, he offered to help Sasha Blouse study, though she overlooked him, deepening his sense of invisibility. He joins the Scout Regiment club and plays volleyball, experiencing comical mishaps like blocking a ball with his face during practice.

The summer festival intensified his emotional struggles. Pressured by Reiner and Ymir to confess to Annie, Bertholdt devised multiple failed attention-seeking plans. He eventually mustered a hesitant invitation for Annie to join him at his die-cutting booth. While she accepted, he failed to confess his feelings, leading friends to mistakenly believe they had started dating. Further attempts to connect with Annie – showing off abdominal muscles or attempting animal sounds – resulted only in awkward rejections or indifference, highlighting his persistent self-doubt and unrequited affection.

His relationships define his experiences. Reiner acts as a supportive, almost brotherly figure, encouraging Bertholdt's confidence. Ymir provides blunt love advice and pushes him into uncomfortable situations involving Annie. Despite his quiet nature, Bertholdt engages in group activities: assisting at a school festival maid café and joining a band for the Battle of the Bands, where his off-key singing unintentionally disrupted performances. These dynamics solidify his role as a well-intentioned but perpetually hesitant member of his friend circle.