[SPOILERS] Different kinds of Mari

[Arzeith-Tau]

So from what I see throughout the story, there are different kinds of Mari

1. Headspace Mari
The Mari that you see on every picnic blanket in Headspace, the one who embodies the good memories about Mari who is always supportive and loving, but has to never leave the picnic blanket for her own safety.

2. Spirit Mari
Black and White looking Mari who embodies the kind and loving Mari that has passed away. In real world, her spirit actually exists, trapped within the grand piano, which is why the grand piano is seemingly clean, free of dust and plays itself when Hero visited Sunny's house, and also why before that, Sunny seems to always refuse to ever enter the grand piano room, because her spirit is there. Despite the terrible thing that Sunny has done to her, she felt guilty that she is partially responsible for the incident, that she has pushed Sunny a bit too hard on perfecting the recital.

3. Something Mari
Maris apparition that was born the moment Sunny glanced at her hanged body. Embodies Sunny's fear of the truth of what he has done to Mari and his creeping guilt. Seemingly always watching and is everywhere, and in real world, always following Sunny behind him.

4. Horror Mari
Every apparition of Mari where she looks absolutely twisted and terrifying. Embodies... death, the feelings of fear so intense that it's killing Sunny inside. Might be the more aggressive form of Something Mari.

There's a particular scene that really intrigued me during Two days left, when the thick fog transpired across the Vast Forest. Omori woke up alone in the neighbor room without the gang. You can interact with the door towards White Space, only to see the Something Mari standing alone inside the White Space, and then proceed to lock the door. I think at this point, you're not really playing as Omori inside the dream world, but actually as Sunny. Omori is never afraid of any of the Somethings, but Sunny is always terrified of them.

Normally Omori would wake up inside the White Space whenever the dream world starts. Could it be that Omori is also part of the Something Mari itself? The one that embodies fear of the truth and guilt, because Omori always want to make sure that Sunny is always afraid of facing the truth and lock himself away from it, while at the same time always insinuate that Sunny deserves punishment by death, by pushing him the idea of suicide, be it stabbing himself or falling from a very tall place. In the final battle, the Horror Mari apparition emerges from Omori himself after not succumbing three times, and his attack that inflicts Sunny with Afraid status and locking him from using his skills appears in form of Horror Mari.

I'm not very good at making my own observation so I want to see more story theories lol.

[DR. DEADHEAD]

Originally posted by Arzeith-Tau:

Could it be that Omori is also part of the Something Mari itself? The one that embodies fear of the truth and guilt, because Omori always want to make sure that Sunny is always afraid of facing the truth and lock himself away from it, while at the same time always insinuate that Sunny deserves punishment by death, by pushing him the idea of suicide, be it stabbing himself or falling from a very tall place.

I consider myself not good at observations either, but I think this is possible at least.
Like you said, I also interpreted Something as Sunny's immense guilt of what he did and the fear that would come with people knowing; that's also supported by one of the endings where we see Something follow Sunny into the car with his mom, implying that he'll continue carrying that guilt with him.
With that, I see Omori as embodying Sunny's memories before the accident, a time where he was happier. Sunny uses Omori and Headspace as a form of escapism from the reality of what he did, so it makes sense Omori wouldn't want Sunny to overcome fear and face the truth as to never leave his one safe space where everything is okay, thus shutting himself away from the real world. When you look at it that way it's plausible to say that both Something and Omori are Sunny's enemies.
Again, not very confident in my ability to interpret stories but it's just what I took from it lol

[lessthanoff]

I always saw the "Horror Mari" as what she truly is now, in the real world. As gruesome and horrible as it is, Sunny may occasionally be seeing Mari as the rotted, mangled corpse she currently is all these years after her death, to further heighten his guilt, since it was his actions that led to her being that way.

If he hadn't lost his temper; if he hadn't pushed her, she would still be alive and would still look like his loving older sister. But his actions quite literally turned her into something hideous and awful - something that continues to fester and become more rotted and horrifying as time goes on (like his guilt).

Again, a gruesome interpretation. But it's the first thing that really jumped out at me when I thought about that image of her, and it stuck with me.

[RGB]

By luck , a movie called "the grudge" aired on tv as I was playing Omori. To me, horror Mari actually embodies Sunny's fear of being ressented by Mari even after her death.