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The mural depicts some kind of alien, hugging an entire community of humans. The alien was drawn as a CIRCLE with all the humans inside that circle. Also, there's another detail of human remains worshipping the mural.
Could it be that Mori was somehow a part of that (possibly abusive?) community which is why he has a trauma of circular light/thingies? Although it could be very possible also that it's just a coincidence.