From J-Wiki

Hiroshi Kuramato, AKA Kayo, is a member of Brigade.

Kayo hails from Asaka, Japan. He worked extensively with Battlestone, Lethal and Boone before the creation of Brigade, as mercenaries specialising in covert operations and wetwork. Kayo was effectively Battlestone’s second in command.

One of the major missions of the Battlestone/Lethal/Kayo/Boone team was the assassination of the big man of the Japanese underworld, Mr. Soroyama. Though this was originally a covert strike, Battlestone used this feat as publicity within the mercenary scene, and succeeded in raising their profile considerably rather than toil deep in the shadows as they previously did.

The mercenary quartet parted ways after a botched operation for Jacob Marlowe, who had hired them to steal a power orb kept within a Youngblood facility. Kayo decided to stick with Battlestone despite his order to leave, but Lethal and in particular Boone left on poor terms.