Unfortunately, it's not possible to do that :( I don't even know how to use renpy (I've only ever completed 1 basic tutorial project for it that gave me a headache so I decided it wasn't the tool for me x3) so to make anything in renpy would mean me having to learn how to actually use it first.
And then I used to use Tyranobuilder, but stopped using it a long time ago after making my first couple of games with it because of how clunky and buggy of an engine it was >.< I imagine it's probably improved by now with a few updates, but still, it's a frustrating and slow engine to use. And even if it wasn't, remaking anything of this length in another engine would take ages :( and I probably wouldn't be able to replicate most of the effects either since they were made using Unity's particle system.
If it were shorter, it might be more doable, but even just the demo is already too long to do it, and the full game will be a lot longer >.<