Starting (obviously) on the 31st and lasting up until Sunday, 3rd, all of Kiseki will turn into a massive forest.
The main island will still have the Welcome Center, although its usual egg-shape will change for that of a pumpking for the duration of the event. The housing facilities will be missing, but around the middle of the island, characters will be able to find an ancient-looking castle, half in ruins. There will be a few items like blankets, some clothes and even a few pots and utensils scattered within it, so feel free to fight each other over them. Towards the east side, there will be a small river leading all the way to the beach.
Other islands will still be separated as always, but the usual hotels, shops, and other things will be missing, to be replaced with the same misty woods.
There will be lanterns illuminating the place, as the woods can be come dense enough to block the sunlight during the day. And be careful if you're in the main island, as straying too far east or west will mean ending up in what were the regular forest areas, meaning encountering monsters is a possibility. In the other areas, regular animals will be found and be available for hunting, although they might be more aggressive than you'd expect.
In addition to all of this, a replay of the Ghost of the past event will take place. Rather than engulfing the entire area in fog, it will only occasionally appear and not be set to any specific area.
That's about it! As always, feel free to ask any questions o/