Many walls have mirrors on them, and Usotsuki can peer at her reflection, which shows her with a black hole for a face. This has some implications regarding her self-view. Mirrors can be broken with the Nail bat, and if the player hits enter twice, mirrors can teleport Usotsuki around.
Reflected in a certain mirror is a doorway that is hidden from the players view. This door takes you to the second part of the Painted Hall which in turn leads to the White Plains. Going inside a face's mouth leads to the White Tiles Path, which connects to Red Bubbles Maze.