Knights of Sidonia / Nihei, Tsutomu

"While the Sidonia girds up to take the battle to the Greater Cluster Ship, a lethal threat that has been brewing within the family erupts"--Back cover.

"A lone seed ship, the Sidonia, has arrived in the Lem star system, ten centuries since the obliteration of Earth. The massive, nearly indestructible, yet barely sentient alien life forms that continued to pose an existential threat are now aided and abetted by humanity's best scientific mind"--Back cover.

Captain Kobayashi becomes commander of the seed ship, and Tanikaze gets a new house in it.

The war with Gauna continues, a humanish Gauna is analyzed, and secrets are revealed about the Sidonia.

Even though the "Sidonia" has gained significant advances in technology, the seed ship still seems out matched by the Gauna, who adapt so rapidly that physical science may not be able to keep up--something more drastic is needed.

A forbidden room is unsealed and all at once the heroic pilot Saito discovers a deceptive avatar of his onboard. Then, an incoming asteroid forces the "Sidonia's" mobile units to enter a positive-gravity environment to skirmish. Assistant Commander Yuhata Midorikawa's mettle is tested.

Tensions rise as some crewmen on the "Sidonia" feel that it is humanity's aggressive posture towards the alien Gauna that has made the Gauna so hostile against them. Meanwhile Hero Tanikaze and his friend Shinatose are promoted, just when the heir of the Kunato family succumbs to dangerous experimentation.

When the Sidonia engages a new type of Guana that is winning the war against the young pilots, rookie pilot Nagate Tanikaze devises his own plan of attack to protect his squadron. Meanwhile, the history of the Guana is revealed and Tanikaze encounters a jealous rival.

Nagate Tanikaze finds himself living in the bowels of the lone seed ship Sidonia ten centuries after the destruction of the solar system, but after he emerges from the Underground he is given a priceless gift by the ship's female captain.