Known to A.E.G.I.S. intelligence as "Shadow", Kageyama wields a Minus Gate, which is the reverse of the normal (Positive) Gate.

Spoiler

Traumatized at a young age by many tragedies in his family, his original Gate of Foresight was warped into the Jet-Black Gate of Darkness. The Gate of Darkness allows him to do many things unavailable to the other Gate Keepers. For example, he is able to transport objects, change his outfit and perform a variety of attacks. He possesses clairvoyance, which the Commander theorizes helped him open his gate initially by allowing him to 'Grasp a future beyond his reach'. A formidable enemy, Kageyama's secret identity is not discovered until it was too late, even though he had been befriended by Ukiya as a student of Tategami High School. In the anime, his real name is revealed to be Yuji Mitsuoka, the son of a rich man who was duped by one of his associates. He returns in Gate Keepers 21 as a middle-aged businessman working for A.E.G.I.S. Network, and is seen riding a blue TVR Tuscan. He is missing several body parts such as his arm, leg, and internal organs due to the overuse of his Gate.

(Source: Wikipedia)