So far I'm enjoying this game. I like the various characters, the art is good, and its an interesting gameplay idea.
I read your post about performance on itch.io, and I have a few suggestions. Not as good of suggestions as I'd like, but suggestions.
The simplest would be forcing the user to only save to disk, since that is essentially of arbitrary size. This is unfortunate as it requires 'downloading' (though, its generated on the page so it won't cost any data limits and will be constrained by their device speed rather than network), and then 'uploading' for saving and loading.
Then there's putting your twine game into a Electron/NWJS instance (a stripped down browser, but gives you more control) and distributing it like that. This would allow file access. Then you could have a saves folder and check that for existing saves to provide the same UI. Sadly, I don't think Sugarcube supports this. So, extra development work and it would increase the download size a significant amount to include Electron/NWJS. I did look to see if you could expand the localStorage size in Electron so then no modifications would be needed, but I failed to find a good method. Also has cross platform issues due to different platforms needing different executables, while the current html file can easily be ran anywhere.
Then there are your usual compression methods. Make sure it isn't saving history since you don't allow going back. Try using 'enums' instead of strings for values. Ex: If you have three values ("Easy", "Medium", "Hard") then store them as 0,1,2 and have an object Difficulties that has the keys 0,1,2 defined to the strings. That way you only store a number rather than a string. This is more useful in cases where you're using it a lot (so for difficulty it doesn't matter at all since its stored as a variable in like one place).
Sadly, I'm not entirely sure how Sugarcube does its stores since its somewhat complicated to try to drive down space (
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), but if its essentially doing a more efficient JSON.stringify then compression then shortening field names could also help. .fr rather than .friendship. Tedious to do lots of replaces, and more confusing. Technically could be done 'easier' if you can hook/modify saving and apply transformations.