Gelgar was a young man who had brown hair that he styled in a pompadour. He had a prominent nose, and wore the traditional Scout Regiment uniform with a gray button down underneath.
Gelgar is one of several soldiers including Henning, Tomas, Lynne, and Nanaba, that are brought by Miche to oversee a group of potentially untrustworthy Scout Regiment recruits. The group is assembled close outside of Wall Sina, and disarmed of their weapons due to the suspicions that one of their numbers might be an accomplice to Annie Leonhart.
Before an investigation can begin, Titans appear within Wall Rose. Miche orders the group to split into four squads to warn the nearby villages; Gelgar is placed in charge of the South team. They eventually make their way to Ragako village, Conny Springer's hometown. After noticing the lack of blood and bodies, as well as the stable full of horses, he and Lynne try to keep Conny's hopes up about potential survivors. He then leads his team to investigate Wall Rose for breaches, but rejoins with another group coming from the opposite direction; who also found no signs of a breach. As night falls, the two groups take refuge in Utgard Castle.
Utgard Castle soon comes under attack from numerous Titans capable of moving during the night. Since the soldiers who had been under suspicion do not have omni-directional mobility gear, Gelgar and Nanaba take the lead in engaging the Titans. However, Gelgar quickly runs out of swords and, after sustaining a head injury, loses the strength to continue fighting. He falls off the Wall and is thrown into one of Utgard Castle's rooms by a Titan, after Nanaba intervenes trying to save him. Spotting a bottle of alcohol on the floor, Gelgar is happy that he will at least have a final drink before dying; however, the bottle turns out to be empty, and Gelgar spends his final moments demanding to know who drank it. A Titan then reaches through the opening and eats him.