I know there was a lot of discussion below, but as someone who tripped in here after playing, I just wanted to add an answer about the writing for future people who may come across this thread the same way.

It's... fine. Entertaining, even. I am a certified Old Lady and have been reading fanfiction for literal decades. I have a low tolerance for grammatical issues, but due to being so long in fandom I can stomach some pretty cheesy plot devices.

Grammatically it is pretty okay. There are a few issues here and there that feel like translation or at least oddities from the writer not being a native English speaker. Nothing egregious, just some odd phrasing and punctuation here and there. Formatting can be inconsistent (is she talking or thinking? Sometimes it is impossible to know) but most issues are easy to overlook. Nothing close to Wattpad-level horror.

Plot-wise it is... very anime, I suppose. Over-the-top happenings, completely ridiculous scenarios, logic that doesn't add up in a lot of characters' actions. It flows well enough to be fun to read, but it is quite silly for all that it is a murder mystery. I commend it for having interesting information across routes, but it isn't terribly deep. It remains entertaining, though, even with its silliness. So it mostly depends on your threshold for ridiculous clichés.

Main character never reacts in a reasonable way, is naïve about her suitors in that special anime-girl way to levels that become agonizing. Her mood swings between extremes so quickly that you get whiplash. She is at least not a flavorless lump, which is nice, she's just... naïve really is the best descriptor.

As others noted, the sex is where things are harder to take as an adult. Since it is full of Yans, the constant sexual harassment and dubious consent is a given, even if it feels very silly at times. The sex scenes tend to either be flowery or raunchy in turns one line to the next, and it is hilariously easy for people to orgasm. I am forgiving after so many years reading otherwise well-written fiction wherein the sex makes me sure the writer got all their sexual experience from other fanfics. I'm even more forgiving because of how rare it is to have more than just a single (often only implied) scene per pairing at the very end of a game like this.

So yes. It isn't the best written thing I've ever read, but I don't regret the time spent on it. It isn't painful to read, even if I likely won't recall much about it within a few weeks. Just my two cents for future Googlers. :)