Excellent game.
Normally I split my reviews into good/meh/bad but frankly, there is nothing that I would consider bad about this game and I have only very minor points that could belong in the "meh" category so this will be mostly me gushing about how much I love this.
First, the artstyle is gorgeous and really helps bring the characters to life. All three of which are really well written. It is genuinely impressive how much you conveyed with very little dialogue, not a single line feels wasted. The characters are also very interesting, I would love to see more of them even though I know that won't happen.
The little tidbits you can find in files, diaries etc also greatly enhance how we see the characters and let someone who pays attention even figure out the "twist".
In general, a lot of games that put you in the middle of the story are very bad at communicating what happened before we as players entered the story. This game does it in an excellent way.
As for the few "meh" points, there is only 4. One, a brightness setting is sorely needed. My computer makes any RPGM game slightly darker and I need to manually adjust my Screen. Then, achieving Ending B is a little obtuse. I believed only the final conversation would affect it, not the other two things. Also, I believe it is a little unclear who the person in the Lab is and it took me two playthroughs to understand that the person in the flashbacks was Dove. And lastly, the final part of Ending B is simply too short. I really wanted to explore the entire area with comments on the past and present.
So all in all, an excellent little game with some of the most efficient storytelling I have ever seen from a game. A lot of rightfully very popular story-based games can't hold a candle to this.