Authors Notes: Okay I'm writing this short one shot because I recently saw the first episode of season two again and it got me thinking. There are four years of Setsuna's life we really know nothing about. I figured the intervention on the Colony Proud couldn't have been the first battle he fought during that time. So this story takes place around two years into the four year time gap between seasons one and two.
2310 A.D.
In the darkness of space an A-Laws transport ship moves slowly, it's left and right flanks protected by GN-X's. Not too far away, camouflaged by an asteroid field, a small shuttle waits. Its lone occupant floats in the cargo compartment. The raven haired young man once known as one of Celestial Being's Gundam Meisters opens his eyes and stares up at his machine. The GN-001 Exia, once an engineering marvel, the pinnacle of mobile suit development, stood before him now as only a shell of its former glory. The devastating battle with the Union's ace pilot Graham Aker had severely damaged the machine. Mechanical bruises covered its metallic coating, the left arm completely missing after being severed by the GN Flag, a camouflage sheet now in its place. Luckily he had been able to recover Exia's head and reattach it but the right eye was gutted, now replaced with a red Tieren optic sensor. The only weapons it has access to is a broken GN Sword and a single beam saber he was able to find.
The now 19 year old Setsuna F. Seiei shook his head, Exia looked about as good as he felt. He knew it wasn't smart to fight in this condition but what choice did he have. As the sole remaining member of Celestial Being it was his duty to continue to try to rid the world of war and evil. At the thought of A-Laws anger courses through his veins. They had taken it upon themselves to become the world's supposed keepers of peace. Setsuna knew better though, that beyond this front lies a calculating organization trying to take control of the world through sheer force and cunning.
A proximity alarm interrupts his thoughts as the A-Laws transport ship has finally come within range.
With one final look at the machine that changed his life, Setsuna climbs up into the cockpit and the Gundam comes to life. The hatch to his shuttle opens and Exia moves swiftly into the darkness of space, leaving a faint trail of light particles produced by Aeolia Schenberg's masterpiece, the GN Drive.
He takes up a position behind an asteroid and waits.
This would not be the first time he performed a blitzkrieg attack like this. With the current state Exia is in he hasn't been able to take any large scale offensive action against A-Laws. Destroying small transport ships filled with weapons and supplies at least disrupts their plans. It wasn't much but it was all he could do at the moment. He knows he has to end these fights quickly, destroying his targets before they know what hit them or have a chance to fight back. As long as he leaves no one alive to report back A-Laws has assumed it was Katharon performing these strikes. This suits him just fine; he can't afford to reveal to the world that he's still alive.
He has been observing Katharon's activities from the shadows for the past two years. Led by the excellent strategist Klaus Grad they operate on the same principles as Celestial Being only with inferior technology. With each of these missions he undertakes he knows the odds of losing his life are great. It gives him some hope though that at least if he were to fall there would be someone there to continue the fight against the Federation.
Setsuna watches as the ship and mobile suits approach, waiting until they are almost on top of him before he makes his move. Taking careful aim with his beam rifle he fires a single shot at the GN-X on the left. The shot hits its mark and the machines head explodes. Before the pilot can react Exia charges forward GN Sword locking into place and in one swift movement he cuts the first GN-X in half. The pilot of the second machine looks on in horror as his comrade's machine explodes.
"No it can't be a GUNDAM!"
He aims his beam rifle at the Exia and fires off a few shots. Setsuna is able to dodge the first couple but the last strikes Exia's leg and he is momentarily thrown off balance. The pilot of the second GN-X sees his chance and draws a beam saber charging at the Gundam.
"I'll put an end to Celestial Being once and for all!"
Setsuna's quick reflexes prevent him from being cut in half by the GN-X's beam. He wastes no time in drawing his own saber. They lock blades; the GN-X putting both arms into the swing manages to push Exia back. Knowing he is in trouble Setsuna uses his GN Vulcan to temporarily disorient the enemy pilot. Using the distraction he swings his saber down cutting off the GN-X's arm. Before the pilot can move away he plunges the beam into the machines cockpit and it explodes in a blinding flash of light.
An alert tells him that the transport ship is trying to make its escape. Two shots from his beam rifle put an end to that.
"Mission complete"
As Setsuna surveys the destruction he just caused his desire for revenge, for those he considered as friends, as family is temporarily satiated. He owes it to them to continue to do whatever he can to retaliate against A-Laws, to disrupt the Federations plans. Celestial being may be gone, he may be the only Meister left, but as long as he has Exia he will never be alone.
He will continue to fight.