Along with several of the other suggestions, I have to mention not to underestimate SeatGuru's advice on this plane and especially this route. Your profile doesn't show your status but if elite keep checking back for any any of the 31ABHJ seats, especially around a week before the flight as upgrades are processed. Several other threads have covered the benefits/drawbacks of these seats but on the NRT routes they can be a lifesaver.

I've had luck once or twice in taking an "inside" seat on a fully empty row in order to try and dissuade others from taking the two seats on either side and luckily it's worked but by no means is this guaranteed. If you're flying with a companion this strategy can be even more effective although still not guaranteed. Good luck and enjoy Japan!