Durch Takaos Opfer wiederhergestellt und gestärkt, macht sich I-401 mit I-400 und I-402 im Schlepptau in Richtung Amerika auf. Die Schwesterschiffe stehen sich schließlich in den Gewässern vor Hawaii gegenüber. Die Zwillings-U-Boote stellen nun keine Herausforderung für die verbesserte I-401 dar, die durch fünf Mental Models und Gonzous strategischen Fähigkeiten unterstützt wird. Aber Iona will sie nicht verletzen.
On their way to Hawaii, their next stop of their journey to deliver the vibration warhead in San Diego, the restored and upgraded I-401 is chased by several Nagara class ships that are surprised and sunk when Gunzō orders an unexpected maneuver to sweep them all at once. After the battle, it is revealed that despite losing her physical body, Takao's core is still intact and she is now part of the I-401's systems. However, knowing that they are still being followed by I-400 and I-402, Gunzō decides to confront them. Before the battle, Iona's sisters make contact with her asking for her true intentions but she claims it is too difficult to explain with words. Meanwhile, an imprisioned Kongou breaks free and absorbs Maya along all the other ships arround her. To confound their enemies, the I-401 moves forward along two decoys with increased capabilities, thanks to Hyuga, Haruna and Kirishima's direct control over them. After exchanging some fire, Iona contacts her sisters asking them to stop pursuing them before it is too late but they refuse to comply. When I-400 is about to be stricken by surprise, I-402 sacrifices herself to protect her sister, who despite finding this decision illogical, becomes driven into anger, leading her to fall into a trap set by the decoys and her defeat as well. Despite grieving for her lost sisters, Iona maintains her resolve to follow Gunzō to the end. However, the I-401 is soon after approached by a dozen ships from the American Fleet of Fog at the front, and a massive flying object at the back, composed of several fused ships led by Kongou, who claims that she wlll be the one who will sink I-401.
Après le terrible coup porté à Iona par 400 et 402, deux autres sous-marins de la Brume, Takao s'est sacrifiée pour remettre le 401 en état. Le navire de Gunzô peut alors reprendre sa course vers le continent américain. Mais les deux "sœurs" d'Iona ne sont pas du genre à laisser une proie leur filer entre les doigts. Elles se lancent donc à la poursuite du Blue Steel qui n'a plus d'autre choix que de leur faire face. L'équipage de Gunzô fera-t-il le poids maintenant que le conflit est direct ?
タカオの献身により復活、装いも改めた４０１はアメリカを目指し、４００・４０２がそれを追う。ハワイ沖で向かい合う姉妹たち。新しい艦体を得、５人のメンタルモデルを載せ、群像たち人間の戦略も併せ持つ４０１は、姉妹艦２隻を圧倒する。「私はあなたたちを沈めたくない」。イオナの言葉は空しく波間を漂う。
一方、４００と４０２に艦隊旗艦を解任され、拘束されていたコンゴウは・・・。
千早和伊欧娜元气恢复以后，整个舰队继续向美国行驶，可是曾击沉他们的400和402仍尾随其后。了解了401当前状况后，千早做出了一个大胆的决定即主动迎击400和402，虽然对伊欧娜来说保护千早是重中之重，但与此同时她也不想和自己的姐妹互相残杀将她们击沉，然而她根本无法劝说400和402停止攻击，最终在千早的指挥下，400和402葬身于深海之中。
En su camino a Hawai, su siguiente parada de su viaje para entregar la ojiva vibración en San Diego, la restaurada que I-401, llamado el Ars Nova, es perseguido por varios Nagara barcos de la clase que se sorprendieron y se hundió cuando las órdenes Gunzo una inesperada maniobra para barrer todos a la vez. Después de la batalla, se revela que a pesar de la pérdida de su cuerpo físico, el núcleo de Takao sigue intacta y ahora es parte de los sistemas de la I-401.
