R.C. 1014: A mysterious mobile suit, G-Self, is being pursued by a group of space pirates and the Capital Guard. The suit is captured by the pirates and the pilot of the suit, Raraiya Monday, is captured by the Capital Guard. A week later, a class of Capital Guard Academy cadets are riding a Crown transport module up along the orbital elevator, Capital Tower, to reach space where they can conduct their first live mobile suit training. On the way up their Crown is attacked by space pirates and their mobile suits, one of which is the G-Self. Bellri Zenam, the youngest of the cadets, pilots a maintenance mobile suit to hold off the G-Self and helps capture the pirate suit as well as its pilot, Aida Surgan.

Capital Territory is attacked by a squadron of space pirate mobile suits led by Cahill Saint, who wants to rescue the captured Aida. Bellri and his friend Noredo manage to rescue Aida as the structure she was being held in was damaged during the attack. Tasked with piloting the G-Self to repel the pirate attack, Bellri kills Cahill in an act of self-defense as Aida watches.

Piloting the Montero, space pirate ace pilot Klim Nick tries to once again assault Capital Territory in an attempt to rescue Aida from its clutches. As the battle breaks out, Bellri, Aida, Noredo, and Raraiya happened to be in G-Self's cockpit while testing their abilities to pilot the mobile suit. Aida succeeds in wrestling control of the G-Self from the others, who remain in the cockpit as she escapes from captivity with Klim.

Klim and Aida return to the space pirates' mothership, the Megafauna, with the G-Self, along with Bellri, Noredo, and Raraiya, who are held hostage. Meanwhile, the Capital Army, the Capital Territory's new military, is officially unveiled to the public and its first mission is rescuing the hostages from the Megafauna. Bellri, wanting to protect Noredo and Raraiya, pilots the G-Self to put a stop to the fighting, but ends up being forced to defend himself from the Capital Army mobile suits and he successfully repels their attacks.

The Capital Army unveils a new mobile suit, the Elf Bullock, piloted by the mysterious Mask, who leads a team to once again attack the Megafauna. After having gained the trust of the Megafauna crew, Bellri also promises to Aida that he will protect the ship in order to make up for his killing of Cahill, and once again helps fight off the attacking Capital Army mobile suits. However, Bellri and Noredo reveal that they are secretly spying on the pirates and have a plan to escape with the G-Self.

The Megafauna launches into space in order to create a distraction for the passing Amerian Space Fleet. Dellensen Samatar, Bellri's old instructor at the Capital Guards, pits an Elf Bull to leads a squad of mobile suits to once again attack the Megafauna to try to rescue Bellri. Unbeknownst to Dellensen, the G-Self was actually piloted by Bellri, and the two engaged in combat. The two eventually discovered each others' identities, but it was too late as Bellri shoots Dellensen's Elf Bull down, killing his old instructor in the process.

The Megafauna launches a decoy while waiting for resupplies. Meanwhile Bellri's mother notices the Capitol Guard have taken over command of the space colony, she plans to escape to Earth to join her son. On Earth Klim Nick decides to take out the Montero and G-self piloted by Raraiya to test her abilities. During this flight the Mask Corps launches their next attack. Bellry, who now has to pilot a standard Mobile Suit in combat, manages to save a helpless Raraiya and retake control of the G-Self. The battle ends in a draw when the Mask Corps retreat when Space Pirate reinforcements arrive.

Mask's forces pull away from attacking Megafuna's mobile suite due to the sudden attacks by the appearance of a Amerian mobile armor. Ameria army of Mick Jack's test machine, Armorzagan, holds off Mask's Forces as Amelia Army inspector general Gusion that appears with supply force traveling to the Megafuna. Bellri to be surprised to know that it is the father of Aida. The Inspector General's supply task force refit's G-Self's damaged flight pack with an experimental flight pack called the "Tricky Backpack", which gives Bell's G-Self new capacities to interfere with a mobile suit electronics. Aida's takes her G-Arcane is regulated to the escort her father by riding with his's transport aircraft. However, she suddenly abandons her father when they detect an emerging of unidentified machine intercept from Capital Tower direction. Mask struggled against the G-Self's Tricky Pack equipment, find himself having to abandon the battle. Meanwhile, Aida pilot's her G-Acrane to limits of her machine's flight capacity higher altitudes try to intercept unknown boogie. Unknown to Aida the unidentified machine she is tring to intercept is Bell's mother. After conclusion of the battle with Mask, Bellri rushed G-Self to aid Aida, but soon discovers inbound orbital glider is his mother. Bell manages to restraint Aida and catches the glider and brings it safely back to the Megafauna. Capital Tower Operation Director Wilmit Zenam (Bellri's mother) meets face-to-face with Gusion on Megafauna, is given her explanation of his nation's motives as possing as pirates and reviving forbidden technologies. Zenam find it hard to believe, however Aida presents photos of illegal actives accruing around the Moon. Wilmit becomes distract and tells Bellri and the other former kidnap victims that their returning to the capital. Elsewhere, Manyi who was aboard the Garanden is a recruit of Capital Army and serves as volunteer on the warship. She encounters Captain Mask after arriving from his defeat. Thou he does not admit it, but Manyi becomes aware of Captain Mask's true identity.

The Megafauna makes an under the radar approach to Capitol City to start a dialog between the two parties. A short fight between the mobile suit with Mask and Bellri in G-Selff ends in another loss for Mask. After hiding the Megafauna in the Jungle a small unarmed sortie group departs for Capital City.

The Megafauna prepares to launch into space and is attacked by new Capitol Guard mobile suits called Wuxia. The Wuxia's mission : to retrieve Bellri, Raraiya and G-Self from the Space Pirates. Arcane, supported by deflected Capitol Guard Catsith mobile suits, tries to defend the Megafauna. Miss Aida, piloting Arcane, gets into serious trouble when a Wuxia completely overpowers her and the Arcane. She is rescued by G-Self deploying a new prototype ground offensive pack. Director Wilmit Zenam (Bellri's mother) is heading into space together with his Holiness. Also onboard is Mask who has a mysterious meeting with the science program director. Meanwhile the Capital Space fleet launches to engage into battle in outer space.

With both the Capital Army and the Amerian Army greatly boosting their space forces as well as the perceived threat from the moon, a space war is brewing. A squad of mobile suits from the Capital spaceship Garanden, led by Mask, sorties to attack the Megafauna in space, but was fended off by Bellri and the G-Self.

The Amerian army fleet engage the Capital Army in battle. After withdrawal of the Capital Army forces, the Amerians quietly take over control over the top of the Capital Tower. However, unknown forces from the Lunar orbit attack and destroy one of the Amerian Army ships.

A delegation from the lunar forces is heading to the Capital Tower to state their demands. Faced with a common enemy the Space Pirates, the Capitol Guard and Captain Mask join into an uneasy allience. Raraiya seems to calm down when she recognizes a house inside the Capital Tower. The allied forces decide to head to the far side of the moon to investigate the origin of the Lunar colony and the danger it represents.