Nagate and the other pilots confront the three Guardian-like Gauna and during the fight, Nagate retrieves a human-like Gauna sample from one of the enemy vessels, that communicates with them through radio with Shizuka's voice leading Kunato to panic.... (more) Two of the Gauna are defeated, but the remaining one, later nicknamed "Benisuzume", retreats. After the battle, the pilots mourn five of their companions who were KIA, while Captain Kobayashi is confronted by Lala over her orders to have Nagate sortie on every mission, knowing that it may eventually lead to his death. Kobayashi then reveals that Nagate is immortal, and by not being a member of the Immortal Ship Crew that rules over Sidonia, he was seen by the other Immortals as a liability, but she claims that by having the skills of their late friend Saito, he will not die so easily. As Lala returns to the dorms, she reminisces about the events of the "Fourth Defensive War" 100 years ago when all citizens of Sidonia perished during a Gauna invasion, except for a few hundred survivors, including herself, Kobayashi and Saito, along Ochiai, who was responsabilized for such tragedy, but not killed because several important files were deleted from Sidonia's archives and relocated to an auxiliary database only acessible through his brain. After the incident, Saito disappeared without a trace, only reappearing 80 years later, aged because he had renounced his immortality. To preserve Saito's memory, Kobayashi ordered the creation of a clone of his, which was in fact Nagate, but Saito refused to have his mind transfered to the child, and kidnaps the infant Nagate with Lala's help, claiming that he will teach him his pilot skills nonetheless. Back to the present, the Gauna sample retrieved by Nagate is revealed to have the same appearance as Shizuka, and while in contaiment, it utters some words including Nagate's name.