S1E1 - Game
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.
April 8, 2007, midnight
S1E2 - Zearth
The children start having second thoughts about the game, but a floating being known as Dung Beetle appears and teleports them to the cockpit of the mecha, which the group later dubs Zearth. On the evening of the same day, a new enemy appears, and Takeshi Waku is chosen to fight it.
April 15, 2007, midnight
S1E3 - Secret
Takami "Komo" Komoda reveals the truth to her father, and while Waku's funeral is being held, Masaru "Kodama" Kodaka is selected to be the third pilot.
April 22, 2007, midnight
S1E4 - Strength
Kodama fights the third enemy without caring about his surroundings, causing many casualties in the process, until he discovers the meaning of losing someone important to him.
April 29, 2007, midnight
S1E5 - Weakness
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.
May 6, 2007, midnight
S1E6 - Lust
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.
May 13, 2007, midnight
S1E7 - Wound
The story of Chizu's relationship with her teacher is revealed, before she is selected to replace the deceased Kako.
May 20, 2007, midnight
S1E8 - Revision
The fourth battle begins, but Chizu is more worried about taking revenge on her teacher than facing her enemy.
May 27, 2007, midnight
S1E9 - Family
Selected to fight the fifth enemy, Daiichi "Daichi" Yamura's final wish is to spend his remaining time happily with his siblings, but his plans are ruined when the battle starts sooner than he expected.
June 3, 2007, midnight
S1E10 - Companion
Bullied by her classmates because of her mother's questionable occupation, Mako "Nakama" Nakarai, after being chosen to engage into the sixth round, resorts to extremes to arrange money enough to complete a personal project of hers in time.
June 17, 2007, midnight
S1E11 - Life
Nagi, a childhood friend of Kunihiko Moji's needs a heart transplant, but so far the only compatible donor found is Moji himself. While dealing with Nagi's drama, he is selected to fight the seventh enemy.
July 1, 2007, midnight
S1E12 - Blood Relative
Maki Ano is in awe as her foster mother is about to have a baby. She hopes to at least witness her little brother's birth, but when she is appointed the pilot for the eighth round, she is left with little hope to be able to do so.
July 8, 2007, midnight
S1E13 - Earth
During Maki's fight, the children discover the true nature of the enemies they are battling, and what really is at stake on every single bout.
July 15, 2007, midnight
S1E14 - Perplexity
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.
July 22, 2007, midnight
S1E15 - Self-Destruction
The ninth round begins, but after witnessing his mother's miserable life, Kirie refuses to fight. Just when his companions are about to lose hope, something that nobody expected happens.
July 29, 2007, midnight
S1E16 - True Identity
Given another chance, Kirie finally decides to face the enemy, but when he surprisingly unveils Machi's identity, a commotion is created among the rest of the group.
Aug. 5, 2007, midnight
S1E17 - Affection
Chosen to the tenth round, Aiko Tokosumi's life is turned upside down when a scandal involving her father brings up turmoil to her household. But she ends up finding in Kanji the strength to carry on with her duty.
Aug. 12, 2007, midnight
S1E18 - Reality
After Komoda was selected for the eleventh match, her father resigns from his position as a politician, but not before revealing the truth about Zearth and the children to the world.
Aug. 19, 2007, midnight
S1E19 - Mother
Tamotsu reveals to Jun Ushiro who his real parents were and tells him their story.
Aug. 26, 2007, midnight
S1E20 - Ego
Machi reveals to the remaining pilots all she knows about the battles, and how she and her brother got themselves involved on them.
Sept. 2, 2007, midnight
S1E21 - Truth
While Kanji fights the Twelfth enemy, the real objective of the masterminds is revealed. Later, Jun receives a proposal from Dung Beetle that may save his life if he accepts.
Sept. 9, 2007, midnight
S1E22 - Distance
Jun takes Kana to her father's house, having Machi traveling with them. On the way, he reminisces about his infancy days, and later, he asks Machi's help to protect Kana from Dung Beetle's intentions.
Sept. 13, 2007, midnight
S1E23 - Snowscape
The human armies decide to intervene during the thirteenth battle, while Machi betrays Dung Beetle and becomes the next pilot in Kana's place.
Sept. 20, 2007, midnight
S1E24 - Story
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.
Sept. 27, 2007, midnight