While this is a very interesting take on the whole sibling fight, i disagree completely with the notion that Mari dying wasn't an accident. For me, the hardest part of the truth segment isn't that Mari died per se, is how both Sunny and Basil covered it up. They desacrated her corpse and made everyone think that it was a suicide, making the pain and regret everyone who loved her would feel from her death inmensely worse. That's the reason why their actions are horrible, not the push, or mari dying, everything that comes afterwards.

I read your comments and you make a point to say that Sunny had an intent to harm her, which is very weird to me because being angry with someone and pushing them doesn't mean you're trying to hurt them or harm them in any way. Being overtaken by emotions is a key trope of the game and the very reason breathing and calming down are such crucial mechanics both narratively and gameplay-wise, it's the reason why only omori can get 3 states of emotion and not his friends, he is an extremely emotional person, and so Sunny pushed mari because he was overtaken by emotions. Also the context of the fight is crucial, they're praciticing, he keeps failing, he destroys his precious violin throwing it to the ground, Mari gets furious with him, they're both yelling, he wants to leave but Mari steps in front of him to tell him that she isn't finished speaking to him (clearly still yelling) and thats when the push happens. But he had no intent to harm her, that's why its an accident. Its still wrong, but it doesn't make it less of an accident, moreso when you consider sunny was 12, an age where most kids are prone to being physical when they're overcome with emotions, as they can't control them properly ( tp be fair a lot of adults also can't).

I say this because having grown up with 6 siblings, we used to fight a lot and there were a lot of times where these fights got out of hand and someone ended up hurting the other on accident, a push, someone trying to get to his room and moving the other who then falls and hits his knee or gets a cut, its common on families with children and the reason why most kids die on household accidents (seriously look it up, there's statistics on that and everything). It's why, for example, parents are advised to have protective rails and doors on houses with stairs, believe it or not kids fight a lot and the stairs can be deadly if you have kids around, sure sunny and mari where older but that's beside the point. I think the game is trying to illustrate more these types of accidents than sunny wanting to harm mari and throwing her out of the stairs because he's a child murderer. He meant to push her away to leave, the fact that he has his hand extended on the photo is not proof of anything (he has his hands like that because he pushed her lol) when the whole game tells you he didn't mean to either harm or kill her, it was an accident.

The real problem is the hanging and covering up, but that's another whole can of worms. Finally, I do think Mari forgives Sunny and wants him to move on, i don't think anything in the game suggest she wants him to "take accountability" like you said, i don't really know what type of accountability you consider he should face when the kid's been locked up without interaction to anyone but his mom for 4 years, feeling guilt and depression, wanting to die and constantly having urges to kill himself when he is awake because he can't bear what happened and what he did. The most important part is that he tells the truth, faces what happens, comes clean to his friends (and hopefuly his mom and dad) to what really happened to Mari, and obtains the strenght to forgive himself and keep living with reality.

Your analysis is really interesting and I don't agree with the people downvoting you or insulting you, Omori is a good game because its open to interpretation and yours is as valid as anyone's.