Photon Batteries, Earth’s energy source, are brought down from space via the Capital Tower protected by the Capital Guard. Bellri Zenam, a Capital Guard cadet, gets involved in fending off
an attack of pirates during his first practical training session, and helps to capture them. He feels something mysterious with the captive girl Aida and finds himself being somehow able to activate the high-performance mobile suit that she calls “G-Self”. Staged in Regild Century, the era that comes after Universal Century ends, the boys and girls advance directly towards the truth of the world through their adventures.
In an attempt to rescue Bellri and the others, Dellensen launches an attack on the pirate corps's Megafauna. Bellri, forced into space combat in Earth orbit, fails to realize he is facing his former instructor and shoots him down with the G-Self.
Meanwhile, the Capital Army demands the return of the G-Self and Raraiya Monday, and deploys first the Mask team's Elf Bullocks and then Becker's Wuxia team. Behind the scenes, a crisis is developing which will drive them all to violate the taboos of SU-Cordism--the existence of a threat from space.