Japan has an effective ban on firearms within the country. The police may carry a weapon - But it's not common, and until a few years ago completely unheard of.
They will, as US police will, carry weapons of other countries. The Sig Sauer and Glock are popular choices there as they are across the globe.
Contrary to other non-gun countries, Japan has actually been one of the few (VERY Few) to actually have decreased crime rates. In fact, the crime rate in their major cities is less than most rural areas of the US.
Major cause of death is still suicide, so don't go gold plating that island yet.
-> Steve