One summer, fifteen kids innocently wander into a nearby seaside cave. There they meet a strange man who invites them to play an exciting new video game. This game, he explains, pits a lone giant robot against a horde of alien invaders. To play the game all they have to do is sign a simple contract. The game stops being fun when the kids find out the true purpose of their pact.
Saving the world is hard.Saving yourself is even harder.Giant robots are invading Earth and fifteen teenagers must figure out a way to stop them. The key to mankind's survival is a towering mecha known as Zearth, but the iron giant's power is not infinite. It gets its strength from the power of life supplied by each teenage pilot. That's a deadly price to pay for someone not yet in high school.
The underage pilots of Zearth are starting to crack under the pressure. In the beginning all they wanted to do was play a fun game. Now they're fighting for their lives and the fate of the planet. Say goodbye to childhood. It's time to grow up and be a hero.
Having no interest in boys her own age, young Chizu develops a crush on her schoolteacher. After a few tentative secret dates, her relationship with the older man takes an unexpected and violent twist. When Chizu finally takes control of Zearth, she's got two things on her mind: save the planet and exact her revenge on her ex-lover.
Zearth's surviving pilots make a promise to each other: they'll never break down, they'll never cry, and no one's to blame. Yet after Maki's battle breaks open the core of her opponent a frightening discovery may test their new resolve. Inside, the children come upon a terrible shock—the truth about who they're being driven to destroy.
Now the children know the truth: their opponents are human beings, just like them. Despite going into his battle with mixed feelings, Kirie finds one more chance to surprise his fellow pilots. Komo follows after him to what seems like an easy victory...until the enemy’s tentacles threaten to overwhelm her.
Komo’s battle takes a shocking turn when the enemy pilot flees for his life...and then comes out of hiding where nobody would have expected. Anko’s battle begins not long after, but this time, the entire world is watching. A broadcast crew from her father’s TV news show comes along for the ride, letting the secret of Zearth out for good.
Through battle after battle, the world has known Zearth as an implacable force of destruction. Now, the monster has a human face, as Anko uses her father's broadcast to deliver a message to the world. An outpouring of support carries the children into Kanji's battle, a test of endurance that may only be won by a drastic, irreversible decision.
Zearth’s next pilot is Kana Ushiro, the one child supposedly spared from the contract that has driven her friends to fight for the survival of their universe. Fearing for her youngest pilot’s chances, Lieutenant Tanaka plans a shocking operation to keep Zearth in the game.
Two children remain to fight for Earth’s survival, and one of them isn’t from this Earth at all. Zearth’s next pilot, Yoko Machi, has been possessed by the mind of a refugee from a parallel world. Before she goes into battle, she and her fellow pilot Jun Ushiro face a struggle of a different kind, as they confront the many victims left behind in Zearth’s wake.
Rule 1Zearth’s battles follow an ironclad rule. If Zearth loses the battle, or if 48 hours pass without victory, Earth will be destroyed, along with humankind and every other living thing on the planet.Rule 2Zearth’s opponents are Earthlings of a parallel world. Victory is achieved by killing the enemy pilot. If Zearth’s pilot is killed, Zearth loses the battle.Rule 3Pilots are contracted in advance. One pilot is selected for each battle. Only the selected pilot commands Zearth. The pilot cannot transfer control.Rule 4If the pilot dies of natural causes or is killed by a fellow Earthling, another contracted pilot will be chosen to assume command.Rule 5After the battle’s end, the deceased pilot’s body is sent home. However, at the pilot’s request, the body may be stored within Zearth, or made to simply vanish.