Conny is very emotional and out going. Even in the worst scenario, he always tries to get everyone pumped. Conny is keen on battle and doesn't shy away for the chance to take on Titans. His weakness: he is not too bright.
Conny is one of the trainees in Trost District when the Colossal Titan breaks down the gate. He is initially unable to escape due to being low on gas, and so joins Armin's plan to break into the supply room and replenish their supply. He is one of the best fighters in the group, and so is one of the seven assigned to take down a Titan in the supply room with one strike. While he fails to kill his target with his first blow, he is rescued by Annie Leonhardt.
Later on Conny is part of a group of Scouting Legion members under investigation by Mike Zakarius under suspicion of being an accomplice to Annie. However, when Titans mysteriously appear within Wall Rose, Mike sends them to warn the surrounding villages. Because Conny's home village of Ragako is in the Titans' wake, he receives permission to join to the group headed in that direction. They find the village seemingly deserted, with no bodies but also no sign that the people fled. In the ruins of his house, Conny finds an immobile Titan that reminds him of his mother. As night falls, Conny and his group take refuge in Castle Utgard, which subsequently comes under siege by Titans.