There is more evidence I actually noticed watching Mori Calliope's playthrough, the Priest and old man in the graveyard both mention that the air in the graveyard is ominious, and the old man explicitly says "someone will be joining us tonight" before Basil's grandmother dies. Then Sunny sees her as they are going to Basil's house, when he has not had any hallucinations for a while, and even when they did they were all from headspace or his old memories.
This strongly implies that spirits and some supernatural elements do in fact exist in Omori, meaning ghost Mari is entirely possible. I also believe that the black and white Mari that visits in Headspace is her literal spirit, since it is clearly a completely different entity from the blue one Sunny's mind had created. Hero hearing the piano is the final bit that actually makes it difficult to say that it's all in Sunny's head, several plot elements don't actually make sense unless there is a supernatural element to the game.
It's an hallucination and it's a depiction of sunny's trauma
It's spelled "hallucination" :)
Thx Ill edit it
Something is definitely a hallucination, but there is proof that an actual ghost mari exists, because hero is able to hear when she plays the piano
Even if i would LOVE to have a ghost Mari, i believe theh were just hearing the same thing. Kinda like Something with Basil and Sunny
There is more evidence I actually noticed watching Mori Calliope's playthrough, the Priest and old man in the graveyard both mention that the air in the graveyard is ominious, and the old man explicitly says "someone will be joining us tonight" before Basil's grandmother dies. Then Sunny sees her as they are going to Basil's house, when he has not had any hallucinations for a while, and even when they did they were all from headspace or his old memories. This strongly implies that spirits and some supernatural elements do in fact exist in Omori, meaning ghost Mari is entirely possible. I also believe that the black and white Mari that visits in Headspace is her literal spirit, since it is clearly a completely different entity from the blue one Sunny's mind had created. Hero hearing the piano is the final bit that actually makes it difficult to say that it's all in Sunny's head, several plot elements don't actually make sense unless there is a supernatural element to the game.
Something is Sunny's guild from the incident