Sisters.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, called the Ars Nova, 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 imprisoned Kongō breaks free and absorbs Maya along all the other ships around 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 Kongō, who claims that she will be the one who will sink I-401.