Okay, I've been trying to hold off on theorizing until I was caught up, but I can't help it. I've had a feeling since the very first happy scene and nothing is going against it so far, so I thought I'd share. (For the record, I'm before Rewrite, but I feel like I've done just about every single thing I could do before that, aside from Chika's events to remain a good homey)
Maya is obviously special. It doesn't seem like this game takes place in reality (as opposed to it being reality seen through the eyes of someone mentally unwell, it feels more like this just isn't real at all). I think most of these characters are just fantasy characters. But Maya is real. Or at the very least, she represents someone real to us. Someone that probably killed themselves. Probably because of us. Because we're a douche bag.
The "Swim Trip" happy scene in particular really strongly seemed to hint that Maya was real and everyone else wasn't. And she's the constant focus of happy scenes in general, which often focus on her dead body. Also there's something buried under our feet. Probably her dead body once again.
My theory is Maya is either our daughter or we're a real life teacher and she was a student of ours. Considering the events of this fantasy life, and his thoughts, it's pretty likely that he sexually abused her and this lead to her killing herself. Then the "jump" at the beginning of the game is him jumping off of a building due to his guilt. And this game would either be his dream while in a coma or his experience in hell.
I've caught wind of some stuff in this thread from later in the game that may throw my entire theory out of the window. But that's what it feels like to me so far.