[Appocomaster]

I might just be ignorant, but do you know the language/culture? It's quite different, and if you don't it could be difficult! I assume you do.
If you go for a year, it'll be a big plus applying to other jobs, as Japan is quite important in some areas of the business world, and the fact you'll have knowledge of an extra language and culture would tip the balance in many job applications where you're otherwise equal.

While cost of living might be high in general, electrical goods are cheaper. If you get things that aren't specific to some zone thing, then it'd be pretty cool in terms of getting nice cheap stuff (and sending it home [/hint])