This felt like the cousin of Milk Inside of a Bag. Yet, you made it your own. Good job on that.
Spoilers ahead!
I expected the story to end with the daughter giving the medicine to her mother, as that was the goal of the protagonist. For that to have been brushed to the side made for an unsatisfactory conclusion from my point of view.
However, it can still be brought up as a later event, since this is a demo. In fact, the mother could become angry at the daughter for taking so long and for possibly getting the wrong medicine. Obviously, she'll interact with her mother again, or so I assume. I get that impression anyway, since the mother and the protagonist's thoughts seem to be the antagonists in this story. Otherwise, I'm surprised the father was in the picture at all.
I really liked the dynamic between the mother and daughter. I liked how although the daughter feared the mother, she still loved her and tried to show it. I liked that. It humanizes their relationship. The artwork of the mother was my favorite, and I felt like it fit the atmosphere and mood of the story the best.
As for the black screens, I didn't mind them. Since it was in the beginning during the intro, it gave a sense of mystery and mystique. Yet, when the black screen appeared in later scenes, I felt you could have used more creepy or unsettling backgrounds to help the reader visualize those moments better. However, this is a demo, and that choice is up to you.
I'm also very glad that this was simply a visual novel and not a point-and-click game or a VN that had many dead ends like Milk Outside of a Bag and Milk Inside of a Bag. That gave me much relief.
However, what I liked about those stories were their cohesiveness in their art styles. Here, the character sprites were bright, vibrant, and popped with color, which contrasted the grainy, muted, and unsettling backgrounds. It threw me off, but I'm assuming such a contrast was intentional.
Otherwise, the story beats felt long with the many explanations involved. I suppose that's the point with the internal conflict going on. Yet, it made the pacing feel slow, and it made the story feel a bit all over the place. Although, it worked in creating a false sense of safety for when the jumpscares came up. So, that's where the long narrations worked.
Although, I'm surprised there wasn't any shake screen effects to add to the drama when the text was big, red, bold, and with many exclamation points. Reading such text felt underwhelming without a sound effect or visual effect to make it more impactful and punchy. Although, it's not necessary.
Otherwise, I really liked the transitions you had in the main menu and game menu. They were really cool! I was expecting there to be a transition of some sort when starting the game, except there wasn't one. Again, not necessary. Just an observation.
Finally, you had some spelling and grammatical mistakes. You would misspell "strength" and said "in the kitchen counter" instead of "on the kitchen counter", among other minor typos. It didn't ruin the experience for me.
Although, the jumpscares gave me some anxiety, but they were well-done and effective. I liked how I could still continue the story and that their presence wasn't a visual cue of a dead end. Thank you for that. I appreciated that.
I also noticed the NEET girl from your other VN, and I really liked that one. I felt like that VN had a stronger story and character, but this one was good, too. In this story, I knew about the girl's problems and her thought processes, but I don't know if I got a sense of herself or her personality beyond that. That's just me, though.
All in all, good job! I'm interested in seeing where this VN goes!