Ominous Grin

Exploration Stage: Post Office
From: Mr. Black
Description: The creepy monster is hiding in the fog and could attack at any moment. Because of this, I've been sleeping badly and having nightmares. In one of them, there was a monster with a flower maw... Wait a minute, is that the maw over there, in the corner?
Completed: This is some kind of phantasmagoria! How could the monster's maw end up here! Hmm, I'm certain I've seen it before, not just in my dreams...