Fifteen children at a summer school program encounter the mysterious Kokopelli and agree to be testers for a game he claims to have completed recently. Soon, they are summoned into the cockpit of a giant mecha, with Kokopelli piloting. Thus the first round takes place.

After the children discover the fate that awaits them, they are assembled and interrogated by the military, except for Isao Kako, who coincidentally is the next chosen pilot.

The children try to find Kako without success, until Chizuru "Chizu" Honda discovers where he is hiding and tries to cheer him up. However, Kako has other plans for her.

Yosuke Kirie wonders if he will find the resolve to fight in the next battle. While Mitsumi starts to look for means to protect the remaining children, Masamitsu discovers her secret.

Jun declines Seki's offer and becomes the pilot for the final round. During the long battle, he reminisces about his fallen comrades while struggling to save the Earth once and for all.