Hey there, I've given a quick go on your demo so I'll be giving some critiques and feedback on it though they might not be useful nor detailed enough so forgive me if I'm not helping ^^;;
First off, congrats on releasing a demo.
Though short it gave some exposure on the characters and how the story's set up. There are some bits that I find unsatisfying but we'll go to that later on. The title confuses me though, which is the main title? 'Promise You' or 'Maiden or Princess'? I mostly take that 'Promise You' is some kind of a catch phrase, a slogan to 'Maiden or Princess'. If so, I think 'Maiden or Princess ~ Promise You' is a more fitting title for the game instead of putting in brackets before the main title.
-The story is a little bit fast-paced. I think that Chihiro should be more uncomfortable both due to the fact that her own parents literally sold her for a job and how she had to move into a new place. You did put in that she thinks too much, no? Perhaps you could insert more of her stating how she feels awkward or something similar in her monologues and maybe making her resent more when her mother gave out the news. Put a little emo moment for her, just a tad bit sadness being expressed about how rough the situation is. I think just a short scene of her in pressure while packing her bags to move out or something might do just fine.
And when she went to go clean the house, maybe changing 'door 1' to 'Room 1'? Haruka did say that she had to clean her sons' bedrooms and using door is like she doesn't know what kind of room awaits her. This one is really a tiny opinion, no need to take it so seriously
Also, try to show that she actually leaves the room after having cleaned them (if she did, depending on the choices). Haruka popping out of no where kinda surprised me ^^;;
I don't think there are any major problems when Chihiro was at school except the fact that the demo abruptly ended when she meets Itoe during lunch and it also ended when that rude boy entered the class. Is it me or the friendly 'demo ends here' message only appears when Chihiro faints? You should probably put that for every endings in the demo, it doesn't make it feel like being slapped with a cut off story (uh, no, I'm not offending you, that's the best I could do to describe it).
And then the supermarket scene, (really sorry I'm pointing out things out of order, I'm not thoroughly referring to the game) I don't get why choosing oranges would suddenly lower the amount of money she had when she bought the apples which were much more pricey if I'm not mistaken ^^;; Instead of making choices between buying food, how about making the choice to whether buy or
not buy at all? That makes more sense to me.
Last thing, don't the siblings have dinner together? Why did it feel as if Chihiro and Haruka were the only ones eating for a meal that time?
-The art... I like it especially your colouring. They're so shiiny :3 The sprites though look a little bit messy because of the lineart. I'm sure that cleaner lineart would appeal better. You stated that you're redoing them so I'll be looking forward for the new ones. I admire you for trying to make your own backgrounds, so I take it that those drawn ones were just placeholders? Mochiku's CG was adorable btw <3
Did you put up all the sprites and CGs in the demo or is it just my pc acting up? My computer is really old with crappy systems and stuffs so I think there were some images that I couldn't see including that CG you posted in the WIP where Chihiro was pinned to the wall. Did you put really them in because the whole playthrough felt empty with missing sprites.
-There are a lot of typos/spelling errors. I suggest you find a proofreader and also an editor so that the story wouldn't be too rushed like it is now. I find it irritating that the load button is not available on the preferences menu. It kind of killed me to load something by having to go to the main menu all the time. I think that this is mostly me being an arrogant idiot, but I dislike the font too. It's sort of an eyesore for me to read since I prefer simpler and neat styles. Also, I don't think that it's completely legal to use that BGM for the main menu, unless you got it from jamendo? Correct me if I'm wrong though. And the gallery doesn't work so I guess you're still testing it.
Hmm, I think that's it. Forgive me if I offended you in some way, I mean no harm. Sorry too for some really long ranting, I describe things too much ^^;; Thumbs up for being able to do all this on your own, I enjoyed it
Itoe's my favourite character so far, being the only one with a sprite I've seen but I've always liked the one who's not really involved in the big circle. I like Shou too but I'm a bit wary here. How old are these siblings? I thought Mochiku looked like a small child- A shota is he? Anyway, I'll be checking for updates. Looking forward to the full game, you have my support