Wow. This is... some ride. I haven't completed all the endings yet, but I have reached the last ending of the secret character and read the last chapter of Particles. There will be HEAVY spoilers in this review.
I'm a lover of horror-mance games (*cough* Boyfriend to Death *cough*) myself, so frankly, I don't find the game "too dark" at all. That said, I'm generally not a fan of "gore for gore's sake", so I'm very pleasantly surprised that this game gives purpose and proper explanation to the "darkness" manifested, and it actually spends time developing the personality of our various psycho "love interests".
About the love interests themselves... I like all of them except Sebastian. God, I'm just SICK of Sebby. He's everywhere and you can't get rid of him even if you're on another guy's route. Like, the others are bad too, but at least they have some self-awareness and are at least trying!
Quinn tries to be a good friend (and is one in several endings, such as when he protects Monika and apologizes for misjudging Sebby's character). Also, he's about the most decent character in the whole game, so I have a soft spot for him and am usually more forgiving of his flaws.
Julian tries to protect you (... yes, only in Sebby's route, I know). But he recognizes his own hypocrisy in his vigilante work and kind of, sort of, tries to believe in Monika even after she (accidentally) stabs him. I'm genuinely surprised that he acknowledges Ash as an inherent part of himself instead of blaming everything on his "evil twin".
Brandon tries to make things right by (generally) keeping his distance from Monika, and he seems somewhat remorseful about his sexual abuse of Monika, while acknowledging that he only regrets hurting her rather than doing anything "wrong". Yes, still screwed up, but again, at least the guy is self-aware!
Sebastian ... OH MY GOODNESS. Not only is the guy delusional (like every other love interest), disrespectful to Monika (like every other love interest except maybe Quinn), only cares about himself (like every other love interest except maybe Quinn), but worst of all, he's pathetic. I applaud every time Alexander opens his mouth and rips his twin to shreds. Like, damn it, listen to your brother and grow up!
Who said this game didn't have a happy ending? The ending where Monika calls him on his bullshit and shatters his fantasy, by pointing out how different she is from the "soulmate" he thinks he knows (based on diaries written years ago), is absolute gold. Destroy him, girl! Yes, Monika dies in the end, but at least it's relatively painless! (Wow, how low my standards for a happy ending have dropped after playing this game ...)
The only thing that surprised me and almost made me want to revise my impression of him ... is when he refrains from killing Julian after Julian has driven Monika insane, just because Julian claims that Monika loves him. I did not expect that, which made me like Sebastian a little ... just a little.
One more thing... I really, really like the overarching plot with the Ethereals! I enjoyed a great deal the dynamic between our Ethereal duo Lux and Quispe. I don't think I could get through some of Monika's ... more questionable decisions without their snarky comments. Also, while I fully understand why Monika is the way she is - and appreciate her as our very unlucky heroine - I am still relieved to have Lux as a "female" supporting character with a more outspoken personality and just good old common sense.
(Speaking of common sense ... I sincerely think the greatest irony of this game is that our otherworldly deities seem to have more common sense than our human characters!)
Obviously, this very fact is also part of the plot. This "cluster" of reality is deliberately made so messed up. My guess is that Monika is somehow connected to Allannia, and Casper is somehow connected to Allannia's banishment, and Allannia is being punished for whatever. But who knows?
Overall, I can't believe this is your first game. The project is very ambitious and well done. I can't wait to see what you have in store for us in Remembrance!
(Last point ... Even though I've bashed Sebby to a pulp with a club in this review, I don't really "hate" him. He's a fun character who embodies the "obsession" in the title, and I find his insanity both entertaining and frustrating :) Being able to evoke strong emotions in the reader is always a strength in my eyes, so once again, well done, Arewar!)