Link Cube

The Link Cube (リンクキューブ) is the cube-shaped gateway between Zyuland and the human world, with the link maintained by a set of six miniature cubes known as the King's Credentials. However, this link was broken when one of the King's Credentials was taken, ultimately being given to a young human named Yamato Kazakiri by the Bird Man to safeguard him.

Following this, the Link Cube became dormant with four Zyumen, Sela, Leo, Tusk and Amu being assigned as its guardians, entrusted with a single King's Credential each. Yamato, now a young man, would be brought into Zyuland when his King's Credential reacted to the Link Cube that he had discovered. Meeting the guardians who believed him to be a thief when they discovered the King's Credential, Yamato quickly made his escape through the Link Cube when it was disturbed by the Deathgalien's invasion of the human world, with the four Zyumen in pursuit. The Link Cube was subsequently crippled by the firepower of the Deathgalien, Jagged, resulting in the Zyumen being stranded in the human world.