Kirie: Shuichi... what do we do now?
Shuichi: Kirie... I can't run away any longer. Leave me here. You have to keep fighting. I think son this curse will be over.
Kirie: I can't run any more either. I'm staying with you.
*Their arms spiral together*
And with the spiral complete a strange thing happened... Just as time had sped up when we were on the outskirts, in the center of the spiral it stood still. So the curse was over the same moment it began, the endless frozen moment that I spent in shuichi's arms. And it will be the same moment when it ends again... when the next Kurozu-cho is built where the ruins of the old once lay. When the eternal spiral awakes once more.
- Uzumaki, Chapter 19
Ignoring the words we know three things:
- Both Kirie and Shuichi become spirals at the heart of the spiral curse.
- We know they didn't escape the spiral apocalypse as they became spirals.
- We don't know if they didn't survive (are dead) as they looked like they were alive when we last saw them.
Reading the ending we know:
- Technically they don't/can't die because time is frozen.
- They become spirals for the rest of eternity.
narrated by Kirie, the protagonist implying that she has somehow survived the spiral apocalypse.
This seems like an incorrect assumption. Stories don't have to follow 'logic', such as there being a spiral curse. However the narration is in the present tense and we can easily assume that this is the story Kirie was writing (to memory) or would have written had she not succumb to the curse.