In World War II, during her mid-teens, Tokyo was bombed by the United States on March 10, 1945, which killed both her parents. With a third of the city left in ruin, she was forced to live with her cousin in Yokosuka for the remaining period of the war. After Japan surrendered following the nuclear attacks on Hiroshima and Nagasaki, she and her cousin turned to prostitution in order to survive the post-war period, during the town's occupation by American forces. It was through "servicing" the troops that she became pregnant by Colonel Miller, a GHQ officer under the command of General Whitney. Miller treated her like a wife and she kept a photograph of him, but he ceased contact with her when he eventually returned to America, leaving her with a sum of money.
Her son was born shortly after Miller left, and she named him "Kazuhira," viewing him as her hope of peace in post-war Japan. As a consequence of his father leaving Japan before his birth, Kazuhira was not considered to be a Japanese citizen due to his father being listed as unknown in the family register. His mother then used the money Colonel Miller had left her to open a shop, selling cigarettes for American soldiers stationed in Japan, with which Kazuhira helped out. She also prepared for Miller Miso soup, although he personally thought she added too much salt to it.
Ten years after Kazuhira's birth, his mother fell ill due to a disease she had contracted during her earlier days of as a prostitute. Her illness forced Kazuhira to practically run the shop in her place, and when he eventually left for college in America, he had her placed in a hospital. The disease began to affect her memory, and when Kazuhira returned to Japan four years later, she was unable to remember her own son. Kazuhira later joined the Japan Self-Defense Forces, providing hospital payments for his mother until her death three years later.
Behind the scenes
Prior to the release of Metal Gear Solid: Peace Walker, Kazuhira Miller, also known as McDonnell Miller, was previously described as a third generation Japanese American. However, with the introduction of his mother in the game, this backstory was altered. She is described by Miller during the Briefing tape "Upbringing," in the section "About himself." He also mentions her when sleeptalking in the Date Kaz Extra Ops mission, where he commented that her miso soup recipe always had too much salt in it.