Hey there! I just finished reading the full story, so here's my notes after my first impression (Not as a writer myself, but more as someone that enjoys reading).
I think you've put together a very touching story, covering some important themes, that is fleshed out and has a lot of heart in it. The dynamic between our protagonists feels quite organic, and from their first interaction it is fairly clear they've known each other for some time. Your bits of devlog about the creatures was especially interesting to me as well. To me this whole world feels like it has been lived in, which I think is excellent.
If I had to give any feedback for this, I'd say this:
In my opinion, be more patient about when you reveal information about the characters. You have these flashbacks throughout the story that gives some crucial info about your world (which is a great touch), but I think you give the reader too much info about one of the characters that when it comes back to the present it doesn't feel like a big reveal, if that makes sense. I think if we learned more about one of our protagonists' past actions (and by extension, their motives) later on in the story, IMO the payoff at the end would have been more greatly emphasized. I think you could allude to these things throughout the story to get the reader asking questions, but maybe don't outright tell us so much about the world, what's going on, etc.
Hopefully you keep working on this and consider putting together a new iteration with the feedback you get here, and maybe consider putting some actual art together (tons on the Discord server, even more on itch as a whole). Also probably quite a few composers that could score something to this if it ever becomes an audiobook.
Thanks for sharing what you've made, and keep up the good work :)