Flegel is a short young man who possesses a fairly chubby build. He has short red hair, freckles on his cheeks, and is usually seen wearing a regular gray coat with a white shirt, as well as a pair of black pants.
Flegel accompanies his father and his father's associates to kidnap Eren Jaeger and Historia Reiss. Upon arriving at the warehouse where the two are being kept, the group is ambushed by members of the Scout Regiment, and Flegel is incapacitated.
After Reeves agrees to assist the Scout Regiment in recovering Eren and Historia, Flegel and his father lure two members of the Military Police into an ambush by Levi's squad. After the two policemen are captured, Flegel asks his father if the scouts will keep them safe, but his father is unsure. Flegel is appalled that his father would agree to help the scouts without guaranteeing their safety, but Reeves scolds him, telling him that a good merchant must be able and willing to find and pursue prospective profits, not just immediate gratification.
As they reenter Trost, Flegel has his father stop their carriage so that he can urinate in an alley. While Flegel is urinating, his father is ambushed and killed by Kenny Ackermann. Flegel stays hidden as Kenny leaves the scene, weeping in horror.