The writing here was technically solid, but it's clear that there was a deep struggle with the genre, this being more of a romantic drama's third act wrapped up in some almost-parodical horror wrapping paper. The main and chapter titles seem to really be reflective of the kind of thought that went into it.

Normally, I'd be much more forgiving about that sort of thing, but I'm writing this review as a voter for the Chunin Exam, and I personally give a pretty high weight to "you understood the assignment and executed properly." I don't feel like your team really understood the assignment. You did utilize your "plot device" and a fair portion of your strict prompt, but the instructions to cook horror and not romance or comedy seemed a little lost.

The twist was... interesting, after a fashion. The very first paragraphs of the very first chapter told pretty heavily where the MC's heart was, so the reveal didn't hit very hard, but I know that the line of properly setting up a twist while not giving it away utterly is extremely thin and hard to hit, and that it's usually correct to err on the side of "too obvious". The mother's flabbergasting stupidity in chapter 2 (and presumably that of others), treating some intense supernatural mayhem as a "prank", is also kind of in that band of "not wrong but not executed the best". Horror often runs on having characters being too dumb to live, and we just sort of accept it to an extent, but in order to not just be a hentai this kind of goes a little farther that way than what I'd like to see.

If memory serves, our team was one of the least enthused regarding the horror genre, and if that's the case it shows, but I suppose I should at least credit that there was a real effort to make the mayhem scenes threatening. But I just don't think it landed that well when taking into account WHY this was written.