Hey-o! This is my first time writing an itch.io community post and I have done no research as to itch.io social etiquette, so my apologies if I'm doing it wrong. I played through this last night and wrote my reactions on my friends' Discord server, and since it would be really great if this fangame became something really great, I decided maybe having my thoughts be visible to the developers might increase the likelihood of that outcome. ...If anyone is reading this but also doesn't want to get spoiled for something, this post contains discussion of this demo's plot and light discussion of the Danganronpa trilogy as well. So, in the following order, here's what I found bad, good, and neutral-but-noteworthy about this project so far:

Bad:
-So, I've been reading Higurashi recently, and in Higurashi, reading text you missed is very intuitive because you can just scroll your mouse wheel up to immediately open the text log, then keep scrolling it up to go all the way to the top. When playing this game I was reading the opening scene, asked myself "Wait, how do I read previous text if I accidentally don't internalize something?" and couldn't figure it out. It's obscure and doesn't get tutorialized until you've met Eva. Then when I tried going all the way to the top of the text log, I had to mash W or the up-arrow to do so. If a player wants for some reason to revisit a moment that happened long ago, doing so is not easy for them.
-So, full disclosure, I played on Mean/Mean. I don't think Mean/Mean should be badly designed, though. I believe what I wrote on Discord here was a direct quote of the first statement you need to shoot: "What could have spilled that blood besides a big scary gun?" My two truth bullets were the gun and the knife. It was... quite something when I had to counteract this statement not with the knife, but with the gun, and then was immediately asked "Then if it wasn't a gun, what was it?" and had to select "Knife" from a list. I... hope it's self-evident why? I see what this section was going for, but I think it would have been clearer what the player was supposed to do if the line they needed to contradict was something more like "Why would anyone think the killer didn't use the gun?!" or something. Something that specifically doesn't already ask what was used.
-I also had two problems with the second Non-stop Debate. Firstly, the orange part of the statement goes away before the sentence is finished. Knowing what's being said doesn't happen until after you've missed your chance to contradict what's being said. Secondly, I have no clue why the autopsy report was the thing used to counteract the idea that the killer was the one who had the gun. I was waiting for Damon to explain it to me like protagonists of mystery games sometimes do to players who win by guessing, but then he didn't. Is it that the victim didn't have bullet wounds? The people arguing that the killer was the one who had the gun also knew that. I don't know if maybe I'm stupid here, but I do feel like I can normally intuit what I'm supposed to point out when I'm playing mystery games that have been sold for profit.
-...I also had a problem with the third and fourth Non-stop Debates. Sorry for sounding like a broken record at this point, I guess. It's a very different problem, though: The Agree Points were... so hard to shoot. I've hit plenty of V-Points in my day, but when the word "see" is in a long sentence that's scrolling and swiveling while the camera swivels and zooms, then the entire sentence goes away fast, I encounter difficulties.
-The Closing Argument minigame also felt a little off to me. In particular, having to move your cursor over an unlocked panel before the lock image went away felt weird.
-I feel like I ended up reading the sentence "This murder was very brutal," paraphrased in different ways a noteworthy number of times. It felt especially jarring from the girl who's canonically played Ace Attorney. Every murder ever has involved harming someone until they were dead. When murders are weird, mildly distressing content will ensue. That's just how it is. It's not that big of a deal. Obviously if I saw something disturbing I would be disturbed, so maybe it only felt off to me from the context of sitting in a chair looking at a computer, but it did feel off to me.
-This last gripe is something I'm listing not as constructive critique, but in the interest of full disclosure. To the developers, who might not be the only people reading this, I don't think there's anything you can do about it and I don't think that's a bad thing. I don't like Eva though. I like Kyoko and Maki, both of whom she reminds me of, but I don't like her. Don't know why. If she didn't seem so important I wouldn't even care that I don't like her, but she does seem important. So has every single first victim in Danganronpa history though, so who knows how much this complaint is even going to matter? Not me, I'm just an audience member, not a creator.

Good:
-The art is good. The music is good. Neither are amateurish as all. The voice acting was good. You'll notice that I had no complaints about any of it. All of it was good.
-Having a body discovery in a prologue was a fun surprise.
-I adore Kai. Design-wise and personality-wise, he kinda reminds me of Rantaro? I had no opinion whatsoever on Rantaro though. I adore Kai.
-Cassidy is also pretty fun. The fact that an actual lawyer's participation in her Ace Attorney bit instantly spoiled her mood is interesting.
-Speaking of the actual lawyer, I'm assuming Wolfgang is going to end up playing a "Rival" role, similar to Byakuya, Nagito, and Kokichi? If I'm right... I'd just like to say I really like what's going on here. Damon reminds me a lot of Byakuya, and Wolfgang already feels like "the Makoto to Damon's Byakuya". This is the exact type of thing I'd be interested in doing if I made a Danganronpa fan project: Exploring the same themes from a radically different angle. I love it, truly.

Neutral:
-So... the bad guys hide their faces behind the visages of animals. So does Jett. Huh. Weird. None of the characters have commented on that yet in-universe. I suspect they will later?
-So... Jean and Ingrid both have big muscles. I wonder which one of them will survive Chapter 3 but be dead by Chapter 5. Both would be funny. Neither would be subversive. If I was making my own Danganronpa fan project and including a buff character who wasn't going to die in Chapter 4, I'd make them cowardly and have them survive the entire game. Neither Jean nor Ingrid are cowardly. That's not a bad thing. ...I suppose you could also do a thing where the victim in Chapter 4 doesn't have big muscles, then between Jean and Ingrid, who are both still alive, one is the culprit and one is a red herring. That'd be really fun.
-So... given what I said about loving how Damon is Byakuya-esque and Wolfgang is Makoto-esque, it's a bit niche-muddying that the game includes, and uses a tutorial to push the player towards, an optional route where Damon says Wolfgang is really great. Not inherently bad, but niche-muddying.
-So... I made a joke about this while playing: Damon's reaction to every character is "that person was a freak, I don't think they should have been accepted to this school", but when he meets Wenona and she says "these people are freaks, I don't think they should have been accepted to this school" it instantly sours his opinion of her. Then later when he says "you're all freaks" she says "Um, excuse me?!" and he's like "okay yeah I wasn't counting you". I wonder what's going on there, and what'll happen as the narrative progresses.
-So... one of the worst things I think Danganronpa has done has been the barely-justified inclusion of immature pre-pubescent female characters in its high school setting, especially in combination with overly sexual content throughout the entirety of the series. I love Hiyoko because it's great when characters are awful but redeemable and I love Himiko for her character development and the fact that she's one of the relatively-sane V3 characters who escapes from the mush and survives to Chapter 5, where only relatively-sane characters are left standing. Yes, I do like Toshiko too. ...It's not bad that she's a child in a cast full of adults, but given that she's a child in a cast full of adults, I would have made her a boy or something. I know Project Eden's Garden isn't going to be mimicking Danganronpa's overabundance of sexual content, but the creative decision to include Hiyoko and Himiko is still something I would have tried harder to distance myself from.

Well, those are my thoughts. I'm aware that I'm just one guy, so plenty of these opinions don't matter, and the rest only matter if lots of people agree, but I figured I'd share them anyway. Doing so required the usage of lots of text. Again, I didn't bother to research itch.io etiquette, and again, I'm sorry if that's a big problem. My final message to everyone reading this: Have a nice day and a great life.

In response to your second Bad point, I think Cassidy's argument should be phrased along the lines of: "And how did the killer spill that blood? Easy: He [used the gun] at the crime scene!" In this case, [used the gun] is a yellow statement, and Assault Rifle contradicts this statement, because its truth bullet description indicates that it was never fired. The Knife bullet wouldn't work, because it doesn't refute the fact that the gun is a valid option.
However, I do believe that the game should have a special way to handle statement-bullet combinations that make sense on their face, but aren't airtight enough to serve as a refutation or agreement. For example, if you use the Knife bullet on the statement [used the gun], this should happen:

Damon: "{COUNTER} No, that's wrong! There was another potential murder weapon: the bloody knife, also found at the crime scene. It's entirely possible he could have used that instead."
Cassidy: "{COUNTER} No way! You trying to say some lame knife was superior to a big, scary gun?"
Damon: "It's not a matter of which weapon is superior; the point is, an alternative weapon could have been used!"
Wolfgang: "I think we're getting a bit ahead of ourselves, Damon. Before we consider the knife, let's first establish why the rifle is not a viable candidate for the murder weapon."
Damon: (I see; this calls for a more direct approach. Cassidy is convinced that the assault rifle was the murder weapon. But if I show what state the rifle was in when we found it...)
{Nonstop Debate resumes; no HP is lost}

This should be roughly the pattern that close-but-no-cigar statement/bullet combinations should follow. The game affirms that the logic is sound, then points out a minor flaw which prevents this particular combo from decisively ending the debate, and gives the player a hint toward the correct solution. Ideally, no HP should be lost.