Omori/Nightmare Fuel

Note: Beware unmarked spoilers.

General

 * You can look at a mirror of the friend group in Headspace up to four times. Most of the times, the reflections is normal. The fourth time, you see a Eyeless Face quartet starting back at you with Slasher Smiles.
 * The moment when you realize there is nothing fantastic about this game. All the horrors -- grief turning you into a monster, neglectful parents, self-harm, hallucinations that skew your vision of reality, - are actually real, and what seemed magical was part of a dream world.
 * Sunny's mental health has deteriorated so badly in both routes that he has forgotten to eat, change clothes, or do little things such as brush his teeth. Heck, Aubrey has to remind him that Mari died four years ago because he doesn't want to believe the truth.
 * There are two ways for Omori to exit Whitespace: one is if the door opens to Headspace. The other is if he grabs his knife and stabs himself when the door isn't there. Omori calmly does this when you click "Stab," and you hear a squishing sound. You cannot avoid this.
 * The Reveal that Omori is not the hero of the story. No, he's the villain and the creator of Headspace. He manufactured the Basil quest for two purposes: to keep Dream-Basil from revealing the truth to Sunny, and to make the dreamworld more appealing then reality. And why? Because Sunny didnt want to face the reality of what happened to Mari.

First Segment

 * Seems like it will be a cutesy game, after you help Omori and his friend group rescue Basil from a random monster. Then when they gather in Basil's house, Basil picks up a photo he dropped. He says with confusion that he didn't take this photo, only to go Oh Crap. Then he stammers, "Mari, she's-" before we see the photo flashing and Omori back in Whitespace. We see the photo later during the Truth Segment: it's a broken violin.
 * Sunny wakes up, hungry, and wanders downstairs. Rather, he tries to do that, but a monster called Something appears on the stairs. You can't hurt Something, but it can do damage to you. The only way to get past Something is to listen to someone encouraging you to breathe, and activate the skill Calm Down. All the while, Something stares at you with utter hatred.
 * After getting sick from leftover steak, Sunny hears pounding on the door. You can ignore it and go to bed, or answer the door. Mari's out there, saying she forgot her housekeys. She wants Sunny to let her inside. If you choose to open the door, something comes through the door that is definitely not Mari. It's blue and has an elongated neck. Most players run for their lives and return to bed.

Main Route

 * You activate this route by opening the front door when Kel knocks in the morning. While going to get a present for Hero, who is returning from college, you notice someone familiar: Aubrey. But her hair is pink, she's holding a bat, and she's bullying Basil in the real-world. Kel tells her to knock it off, and she challenges him and Sunny to a fight. Yes, she will use the bat. Sunny can slash her with his steak-knife, which causes her to bleed and leave immediately. Kel gives Sunny a What the Hell, Hero? and confiscates the knife, saying that it's dangerous to carry that around.
 * Humphrey the Whale doesn't seem that bad. Sure, he swallows you, but he says it's so you can get another hint. The friendship group is unaware that Humphrey was using them to ensure that the Slime Girls feed him. When they and Sweetheart fail to do that, Humphrey takes care of them by swallowing them. Then he turns on the friendship group, threatening to eat them in turn.
 * Blackspace
 * The Truth

Hikikomori Route

 * The fact that this route exists, and Sunny never faces the truth. (You trigger this route by not opening the front door when Kel knocks.) Sunny allows Omori to take over him in the real world, and live permanently in denial. It's also implied that because you didn't interfere, Basil commits suicide independent of your actions.
 * There is an Eldritch Abomination named Abbi who doesn't have a real-life counterpart. It's implied Omori locked her away because she didn't want to play by the script.
 * To "save" Sunny from Something, Omori takes over him, and this time it isn't a fight. Sunny surrenders completely to Omori, meaning that he has completely succumbed to the dreamworld fantasy.
 * Blackspace 2
 * Omori either has a memory or a projection, of Sunny's father cutting down the tree where Mari allegedly died by suicide and disowning him. The worst part is we don't know if it's even real or not.