For good decapitation capabilities, we will need a modified turkey arrow. 
Man, Rich.  Someone is having one helluva Thanksgiving.
In any case, decapitation may not be enough. For humans? Yes, that would be enough if you're being attacked by your own. But for zombies, that may not be enough.
True, that there is a lot we don't know about zombies, but we are just going to have to make some assumptions.  I think it's a safe bet that you can kill them by removing or damaging the brain.  Personally, I think a bullet to the brain would be sufficient rather than smashing the whole thing.  
I agree that guns are a poor long-term solution.  I would just like to have one to get as far as the marina.  The good news about Japan is that you're never too far from the water, but the lack of weapons (it's illegal to own swords, too) is going to be a problem.  Though now that I think of it, we do have a few 
castles, which would be quite impenetrable to zombies, and no picnic for armed gangs.  I'll have to mull that one over a bit and get back to you...
More to your question thought, I would suggest you research zombie outbreaks in your geographic area. There seem to be some rather significant differences in the types of zombies you get. For instance, in china zombies hop around with arms outstretched.
That's a good point.  I don't think I've seen any Japanese zombie footage.  Ghosts, yes.  So I do my best to keep my wife happy, so that if she dies suddenly, odds are that she won't die angry with me.  From what I've seen, if you have a Japanese ghost pissed at you, you're boned.  She got her hair cut short recently, which I think is a good sign. 
Of course we get a giant radioactive monster about once a month.  But the mutant high-school girl brigade usually makes short work of them. 
What am I thinking?!  American military base!  I have a passport!
God Bless America.