A captain of the Estovakia Air Force, Kleiber previously worked as a flight instructor for a North Osea security corporation, acting as an intermediary between it and its parent arms manufacturing company. His activities led to the creation of a solid training facility that would birth some of his country's best pilots.
In the Estovakian Civil War, he acted as the captain of a mysterious fighter squadron, being involved in a series of enigmatic operations that included the destruction of a supply base in west Estovakia. However, most details concerning his activities remained uncertain after the conflict.
On February 12, 2016, Gunther was deployed during the Emmeria-Estovakia War to halt the Emmerian advance through the Selumna Peaks, breaking off from the main force to launch a surprise attack. However, he was discovered by the Garuda Team and shot down. His fate remains a mystery.