I see why this won the award. It's quite good, and it looks at gender roles. But, I may have a problem with it.
The premise is that a plague killed off three quarters of the men in Japan, and, as a result, society changed. Men are valuable commodities, as their seed gives women children.
Now, as I understand it, the thing that determines how quickly a society grows is the number of fertile women. If my understanding is correct, then the gender balance should have been getting closer to equal over the next eighty years -- unless the plague constantly sweeps through or other factors continue to kill off the men.
Perhaps this will turn out to be the case, although the blurb on the back of the second volume indicates that the plague has been nearly forgotten, as has the fact that, less than a century ago, society used to be different. Then again, blurbs can be wrong or misleading, intentionally or otherwise.