Kazuhira "Kaz" Miller, also known as Master Miller, was the subcommander of the MSF and is currently the subcommander of Diamond Dogs. He was born in Japan, with his name being the Japanese word for "peace," to an American officer and a Japanese woman. Getting an education in America, he returned to Japan and joined the Japan Self-Defense Forces.
However, while his skills were pretty good, he wasn't rewarded for those skills and would eventually leave the JSDF. After returning to America, he found out his father committed suicide and his mother died from an illness, leaving him to become a mercenary. It is during his time as one that he would meet up with Big Boss in Colombia, although at first as an enemy.