Fratemate, The 'training' periods I have been told about by friends who have stuck with it and got through are as you say eye-watering, especially if you essentially forego any sort of family life whilst sitting through needless red-tape which must be hugely frustrating.
In my current airline if we take experienced Capt's or FO's who are rated on our aircraft type, they are under line training in their respective seat in well under a month, this includes:
Local AIP, law and HPL exam for licence conversion (2 days)
Local medicals for licence issue and residency permit (1 day)
Company OCC ground school training inc aircraft Diffs, SOP's, LVO's, Area Brief, RNAV, Adverse WX, RVSM, TCAS etc (4 days)
Company OCC SIM training, SOP's, handling refresher, LST/OPC, LVO's, RNAV etc (5 sessions)
Ancillary training - initial CRM, SEP, First Aid, DG, Fire/Smoke, SEC, SMS brief etc (5 days)
Company indoc, residency permit issue, HR and license issue. (2 days)
This process in Japan is how long?