The Cube (キューブ, Kyūbu) is a structure built by That Man which is located within the Backyard. The 'Key' to unlocking the Cube are the Prime Gear cells of Justice. The Cube is said to have the power to manipulate the information of the Backyard, allowing it to influence the real world on a universal scale. The Magic Chord Signature of the Cube is stated to be exactly like the Chord Signature of Sol's Gear body, but the significance of this is unknown. During the Baptisma 13 incident, Valentine attempted to obtain the Key to access the Cube, however she was ultimately thwarted by Sol Badguy who returned the Cube to its original form and shattered the door to prevent anyone from entering it.