Ken Yamaguchi is Japanese-American: born and bred in the good old USA. In Sunnyvale, CA to be exact. He was the second son of a set of three, 4th generation Japanese (there is a trace of Caucasian in his ancestry, a grandmother back on his father's side) but as thoroughly American as they come with only a peripheral familiarity with his ancestral roots. In California, this is hardly uncommon. He grew up in the normal way, raised in what was, likewise, a normal way. His parents were music teachers and liberals; his older brother inherited a talent for music, while his younger demonstrated a prodigy's ability with mathematics. The one went to the Paris Conservatory, while the other went to MIT.
Ken, being depressingly average in all respects, compensated for normalcy by getting an average degree (BA) at an average school (UC Santa Clara) and then moving to New York City to work for The Man.
It would not be understating it to say that his career choice — the NYPD — pained his parents, who had hoped for better, safer things for their second-born. For Yamaguchi however, who combined an interest in people with a dislike for officework, the job was ideal. He put his time in as a patrolman, living in a tiny apartment and dating his way through New York City wildlife; after six years, he applied for the detective exam and joined Robbery. Three years after that, he married his Spanish girlfriend of the time, Maria, and transferred to Vice.
From there, it was only a short step to fatherhood and Homicide. Three years later, he did both, becoming the father of a little boy, Christopher. It was a happy time for him and his fledgling family, difficult though things were given the demands of his career.
Two years later, New York went Boom.
Yamaguchi was singularly fortunate, by almost all standards. True, he lost half of his in-laws to the explosion, and a significant proportion of his colleagues. On the other hand, his wife and son were on a visit to California, a family vacation for which he was set to join them when the bomb went off. Pure chance saved his life as well; on the way to the airport, his partner — the driver — caught a call in Brooklyn. Yamaguchi, depending on his badge to clear security quickly, rode along for the fun of it rather than wait at JFK. As a result, he was safely away when the explosion wiped out much of New York City.
The revelation of the Evolved had little impact on him, beyond the rather vague annoyance of a busy man faced with official flummery. The reality check of subsequent events resulted in a quiet struggle between liberal overcompensation — the automatic overreaction towards the side of tolerance — versus the complicated resentment of a cop forced to deal with the aftermath of Evolved-created disaster. It took almost a year for him to achieve some sort of equilibrium, in which cop instincts share uneasy space with humanist ones. Now in Homicide, with his family squirreled safely away in a small one-bedroom in Jersey, he muddles as best as he can through moral minefields, ignoring inconvenient shades of grey where he can.