Block World is one of the 12 original worlds accessible from The Nexus.
Features
The Hat & Scarf Effect can be found here.
The Hat-and-scarf girl lives here. She is invisible apart from her clothing unless the Stoplight effect is used. She teleports Madotsuki to the tops of blocks when interacted with.
The Men's Restroom can also be found here. Despite being female, Madotsuki can use it.
Connections
White Desert - The Hat-and-scarf girl will sometimes teleport to a black portal situated on top of a certain block formation. This portal leads to the White Desert.