If it were the Cognitive World, these things would be a lot more dangerous, believe me.

From what I can tell, this forest is something like..... a threadbare place where the boundary between worlds has worn thin. A world governed by reality, yet where cognition is allowed to bleed through the cracks, like a daydream.

[It's almost like the inverse of a Safe Room, honestly--not that Shido would know anything about that.]