Sorry to put a dampner on this but unless you`re being sponsored by a Japanese Airline it would be all but impossible to work in Japan as a pilot.
For example the JCAB will conduct written exams in English for expats employed by a local operator, however this concession would very likely be unavailable for a self sponsored applicant. So unless you are will to learn the language to the extent that you can undertake a written technical exam in Japanese, forget it.
Further obstacles similar to that already described above await the un-sponsored applicatant at almost every step along the way.
Cheers,
Fark.