Gyunei is first seen fighting Amuro Ray while Char prepares to drop the Fifth Luna asteroid onto Earth. Gyunei was unable to hold his own against Amuro, forcing Char to intervene. The two manage to hold off Amuro and Londo Bell and succeed in allowing the asteroid to destroy the Earth Federation headquarters at Lhasa.
After Quess Paraya defected to Neo Zeon, Gyunei was the one who trained her. Gyunei develops an interest in Quess, but became frustrated by the fact that she was only in love with Char.
Gyunei later uses the funnels of his Jagd Doga to destroy a full nuclear barrage sent to prevent Char from dropping the Axis asteroid onto Earth. He also captured the Londo Bell pilot Kayra Su hostage and executed her when Amuro Ray refused to exchange the Nu Gundam for her.
His ego bolstered by the fact that he destroyed the whole nuclear barrage, Guss begins seeking to surpass Char to prove himself to Quess. He later goes out into battle together with Quess to fight Amuro. Despite facing two opponents, Amuro managed to obtain the advantage in the fight and shot and killed Gyunei with his beam rifle.