Absent foreigner bank account ? (Tokyo)

Hi all
Does anyone know:
If I have made savings while on contract in Japan, but after ending I don't want to exchange because of the current poor rate against dollar, etc. - can I leave it in Japan?
And - with the prospects for further yen devaluation - for how long? (years?)

In other words, are there are banking laws in Japan against foreigners holding accounts without being resident?
And leaving the accounts dormant, maybe for years?

thanx