The Gundam Astray Blue Frame Second G is another configuration of Gundam Astray Blue Frame Second. The "G" in the designation stands for "Gai" and is added to differentiate it from Gundam Astray Blue Frame Second L. Blue Frame Second G is the original upgraded form of MBF-P03 Gundam Astray Blue Frame that Gai had in mind. It features redesigned shoulders and feet designed by Gai himself, while the rest of the MS is unchanged from that of the original Blue Frame.

The new, smaller feet give the MS better jumping power and are mounted with retractable "Armor Schneider" combat knives in the heels and toes, which could be used as kicking weapons or as anchoring spikes. The new shoulders contain fin thrusters to improve the suit's evasion capability, and can also be used to make unexpected sideways maneuvers during battle. Two other combat knives are also equipped on the hips. As Gai wants Second G to be a fast and mobile MS, he discards the physcial shield; he plans to rely on the MS's speed to dodge beam attacks and the antibeam-coated combat knives or the back-mounted beam sabers to battle against other melee beam weapons.