This cube is supposed to be some bizarre aquarium. The white spots and shapes are the fish. They float around and swim aroun like normal fish do, except when you touch the cube. They will then swim to that place and wiggle around in that area until you let go of the cube.
Neat huh? The cube become other colors as well.
You can find this cube by the JR Shinjuku west exit between the Keio mall and the Odakyu mall.
