Hi there! So, I'm actually commenting before playing the demo, but I have a reason! The game is extremely appealing to me, generally speaking (not to mention you talked about Demonheart and that's one of my favorite western indie VN/RPGs), but I found myself intrigued (and in a sense, worried) by the mutations concept.
So, on one hand I love the idea of these transformations, and besides, this seems to be like the kind of game I adore, with a ton of bad endings to collect and that would make the good ones even more satisfying when played last. On the other hand, what I enjoy the most in games with personality stats is having a MC with a VERY defined and often extreme personality, and you said the transformations were "warnings" about that. A warning usually implies the thing it warns against is... well... bad. And I find myself worried I'd be "punished" by playing the way I like to play (so, a very very defined / extreme in their personality MC)...
Obviously I know you can't say much about that without entering heavy spoilers territory so... I don't know, can you tell me ANYTHING related to if I'll be able to get satisfying endings with my playstyle? I know I'll get madly attached if I play even the demo only, and I would prefer to avoid the frustration of not having a single ending that I'd like.
If it helps you in answering without revealing story details (you know, so you can just tell me "you should be okay" or "you may not like it", without details), in any kind of stories about the MC being transported to another world, I like it when they stay in said world (sometimes I get really really upset IRL if they go back to their world, actually - that's legit a content/trigger warning I wish could be included in games!). I also like transformations, as long as it doesn't mean the character looses their mind. I tend to appreciate open endings, but I still do like it when the main couple can be happy together.
Okay, I think that's it. Sorry for the very extensive and weird comment that isn't even feedback, and for the questions. If you'd prefer not to answer at all, that's okay - I'll come back when the game is released and when telling me would be less spoilery!