Having disposed of the opposition, Kobayashi sets Sidonia's course to the ninth planet in the nearby Lem System. All-out war now seems unavoidable.

A new threat appears in the form of Gauna 550, which has ejected countless lesser gauna cores on an intercept trajectory with Sidonia.

Despite being instrumental in their victory, Tsumugi is severely damaged defending Sidonia. Izana, also critically injured, makes a bold decision.

The Sidonia's new weapon test succeeds, but the crew realizes they can't shut it down; Yuhata sends the garde pilots to investigate the disturbance.