@bookbarker
Your point is correct if we assume that the demons learn and subsume the ideas of the humans, or, are purely based off of the imagination of them, but that is not the case here in this manga. The ghosts and monsters are portrayed not as beings spawned from human thought, but separate entities. This being the case, if a specific day is in and of itself a day for when the borders between worlds is weakened, the day itself, Japan should have already had another separate holiday on October 31, since the holiday (that kills humans)would be designated by the spiritual realm, not vice versa.