As a long time resident of Tokyo, I see things going something like this.

Just like everywhere else in the world, a mass exodus from central Tokyo. Only the roads would be much worse off than almost anywhere in the U.S. or Europe. I've attempted to drive out of Tokyo on holidays or long weekends, and traffic can be be at a practical standstill for 30 or more miles in nearly every direction out of the city. I guess we can assume the outbreak happened pretty fast, so it might be safe to assume that the metro area of Tokyo might be better off than the outlying areas and the prefectures nearby. Not that it would be safe by any means, but I think of it as a pebble dropped in a pond; fewer numbers in the center of the city, with waves of zombies spreading out. Of course they would make their way back into the city eventually, but at the beginning you might have enough time to fortify a place to live. There are massive stores of emergency supplies for earthquakes all over the city and underground, so provided you could get to them, you would have enough food to last for decades assuming a large portion of the population has turned. This goes for all major cities like Osaka, Hokkaido and the like.

Going by the reactions of people here after the earthquake last year, I think survivors would band together quickly and form communities, sharing goods and housing, protection, etc. Seeing as there are virtually no guns outside of police revolvers, and a very small amount of assault rifles in the Self Defense Forces (when compared to the U.S.), it would be nearly all melee weapons. Those who live far up in the mountains would be affected much less, and those who live on the thousands of small islands around Japan would be affected very little. There are farms and livestock on most, and populations are small enough to be sustainable. On the small islands, most people know each other and would probably have little problem banding together to clean out the few undead and set up patrols and watches.

Anyway, that's what I think would happen here in Japan.