You will have to have your aircraft approved prior to bringing it in and inspected after the first landfall.
In particular your engine MUST be less than five years since new/factory overhaul regardless of hours clocked. (same goes for instruments)
Only three brands of radios were approved then, these being King, Collins and ARC.
If you have any other brands like Narco etc they have to come out and be replaced by one of the approved brands.
Is this if you want to import and put the aircraft on the Japanese register, or if you're just passing through under another registration as well?
In the latter case, doesn't sound very ICAO of them, does it?