A very sharp shot - her hat in particular is so tactile - and a grim set to her jaw that matches her friend's - they do look like a matching set. I'm tempted to think the cold weather especially gives people that expression. For me the background is a bit distracting - the light is brighter behind her than on her which makes me see that it's a bit off-kilter. I don't that the angle would bother me if you adjusted the lighting a bit more to really focus on her face and hands. That's my 2 cents for the day.
This portrait is pretty much perfect for me. I disagree strongly with Damon about the background light being distracting (no offense intended). It actually helps define (pops) your subject. The light on the rail behind her just leads the eye to your subject. Well done.
What got my attention first was the placement of her hands - I don't know what it is about it, kind of reminds me when we got our photos taken at school they would always make a big deal about how you placed your hands, the guys had to clench theirs into fists whilst the girls held theirs together like your subject is doing here. It's really quite a tender shot, nice work man.
There's something really powerful about this for me. So many things contrasting nicely with each other: the colourful hat and modern metal rails and the traditional style Japanese roof top-right, and the seriousness of her expression. A lovely blend of elements that together make a great shot.
You have certainly capured imaginations with this photo Duncan. To me her expression is a contemplation of things lost; opportunities ... possessions .... loved ones