It depends on the oyabun. Hanzo Shotozumi, who leads the gumi that controls Downtown and the International District, will use women and metahumans "in areas where more traditional kobun are out of their depth or too recognizable."
Sato Kanaga, the oyabun of Everett, Snohomish, Auburn, and Redmond, purged the foreigners and metahumans and shipped them off to the Kenran-kai in Puyallup. Now it's been 10 years since then so anything could have changed, and if the Kanaga-gumi is going to have any elves - which, as you point out, are the most likely of the metahuman races - they're probably going to have them in the Barrens (as opposed to, say, Snohomish). And if they know something is wonky at this location then it's entirely plausible that they would have hired outside help (to minimize risk to their own assets) until they figured things out.
Achak isn't discounting his theory; it's just strike one. And, for the record, I'm not trying to poke holes in your world. I just know this realm a little better than most because one of my other games in a ganger campaign with the syndicates playing an increasingly important role as the gang rises. If you have any plots involving great dragons or immortal elves I will be as helpless and ignorant as a newborn lamb. But in either case it is the GM's world all the way.
