The Story takes place in an alternate reality based in the year 1996, where humanity is advanced enough to develop long-range space travel, as well as bases on both the Moon and Mars. However, the Cold War tensions between the United States and the Soviet Union have not ended; rather, they've escalated as both sides build military facilities in space, and the shadow of nuclear conflict looms over humanity, both on and off Earth.
Meanwhile, on the Red Planet, an exchange program created by the United Nations to promote peace and understanding is about to begin; the "Cosmic Culture Club", consisting of 16 boys and girls, as well as their instructor Elizabeth, arrives at the UN Mars base, and are being welcomed by the staff. Among the passengers is Anna a 14 year old girl who serves as the narrator for the story.
Suddenly, four unidentified humanoid robots classified as Super Powered Tracers are detected, engaged in fierce combat with each other. The UN base is caught in the crossfire and quickly destroyed, killing all but six members of the "Cosmic Culture Club"--Elizabeth, Arthur, Roan, David, Simone and Anna, and leaving them stranded on an inhospitable planet that has suddenly become a battlefield. As the battle ends, the lone SPT standing lands next to the terrified group and opens up revealing a pilot, who simply announces to them, "Earth is at stake".
The robots who destroyed the UN base were the creation of the Grados, an alien race, from the Udoria system, who came to the Sol system for the purpose of conquest, seeing an easy victory as the two superpowers raged against each other to exaustion--however, this could also be described as an act of pre-emptive self-defense; the Gradosian supercomputers have determined that humanity will eventually cease its infighting and become powerful enough to spread through the galaxy, posing a destructive threat to even the far off Grados.
However, there were two Grados opposed to the plan: human astronaut Ken Asuka, assumed lost during a deep space mission but discovered by the Grados, and his son Null Albarto (his "human" name being Eiji). As the Grados prepared their invasion fleet, Eiji stows away on board one of the ships and steals their most powerful and advanced weapon, the SPT-LZ-00X Layzner before fleeing, seeking to warn humanity of its impending invasion. It was here where he was attacked. Aside from the Layzner, the surviving humans have now become very important to the Grados; as the only human eyewitnesses to the aliens and their power, the six are the only ones who can convince the warring powers to stand down from destroying each other, and focus on the greater threat.