The Monochrome Street is an area accessible from the streetlight with two lights on its right side and one on its left in Red Streetlight World.
The Monochrome Street is a large silhouetted area, decorated with large white arrow-shaped objects with their darker reflections visible on the ground. When Urotsuki is on the black background her sprite will be all white, and it will be all black on the gray shadows.
There are also silhouettes of various NPCs in this area, which only appear if the areas where the original NPCs appear have been visited. The silhouettes include a sane Shadow Woman, a Beret Sister and Sweets Musume, among others. These NPCs react to effects the same way their normal counterparts do. For example, the Sweets Musume will jump and chase you around if you use the cake effect, and talking to the scarecrow girl will teleport you to The Docks if the Provost-san mask is currently equipped. Similarly, chainsawing and getting caught by the Shadow Woman will transport to you to the Red Brick Maze.
Three of the large arrow objects have doors on their shadows. One takes you to Red Streetlight World, one to the Shinto Shrine, and one will take you to the Mask Shop, which you can also enter from the back side to view an event.
Nexus → Red Streetlight World → Monochrome Street