As Hiro and most of Squad 13 and the surviving Nines head into space aboard a gigantic Klaxosaur mothership, part of a massive fleet on autopilot to Mars orbit, Michiru stays behind.
Kokoro believes that because she can no longer pilot a FranXX, she has no more purpose, other than perhaps staying by Zero Two’s side as she continues to get remotely cut by the VIRM attacking Strelizia. Since she feels herself so useless, she neither expects or wants anyone burdening themselves for her sake, but Mitsuru won’t hear of it.
A VIRM fleet intercepts Hiro and his Klaxosaur fleet, attempting to block them from reaching Strelizia, who they’re surrounding. But thanks to Nine Alpha being compatible as Hiro’s pistil, and some teamwork on the part of Squad 13 and the other Nines, Hiro is able to blast through the walls of enemy ships and reach Strelizia, which is believed inert due to not having a Stamen.
Alpha gets Hiro to the access hatch, but self-destructs soon after to take out a particularly large, nasty VIRM. The other Nines sacrifice themselves in similar fashion, going out doing what they were always created and designed to do: to fight in battles like this.
Humans like Squad 13 have other battles to fight, whether it’s the fight in which Kokoro and Mitsuru have to start over after losing their memories, protecting one another and awaiting the new life they created, or Hiro keeping his promise to Zero Two.
When he makes contact with her in Strelizia’s cockpit, Zero Two tells him she left Earth so that Hiro could remain a human, and help rebuild civilization with his Squad 13 family. But that’s not what Hiro wants. He wants to be with Zero Two, like they promised they would be, even if he becomes a “monster” like her.
He believes even Zero Two wanted this despite her actions, because she left the last page of her story blank. By returning to her side Hiro is filling that blank page with a new ending, one in which the lovers never part.
Their reunion triggers a major transformation in Strelizia Apath (or Apus, as it’s spelled in the subs this week), its mask shattering to reveal an enormous Zero Two, replacing or transporting her human body on earth into the cockpit with Hiro.
Now fully awake and in her true form, Strelizia unleashes a new and devastating arsenal of weaponry that annihilates the VIRM fleet in moments, likely ending Squad 13’s last military battle and freeing them to begin the next battle: surviving and rebuilding.
However, Hiro and Zero Two won’t be joining them, at least, not for a while. Devices emerge from the Martian moons of Phobos and Deimos, and their combined beams open a warp gate to systems heretofore long out of mankind’s reach (though at this point the couple can probably no longer be called 100% human, what with the horns and all).
The VIRM’s fleet at Mars is destroyed, but their main fleet is still out there, and their mission to enslave humanity and the Klaxosaurs remains in force. Rather than wait for them to threaten the solar system again, Hiro and Zero Two will take the battle to them.
That means saying goodbye to Futoshi, Ikuno, Zorome, Miku, Goro, and Ichigo, as well as Kokoro and Michiru. It would be nice if they could all fight their individual battles in the same place, but it’s not to be, so they’ll all have to just wait and see if Hiro and Zero Two will ever return to them.