So I don't really understand what the Japanese Aviation Authorities are asking for
- 250 hours Pilot in Command on any aircraft OR 70 hours as PIC with the remaining as PICUS/P1 Under Supervision OR 500 hours as PICUS/P1 Under Supervision
It's pretty simple and, as pointed out by Rumbear, is a JCAB requirement to issue a foreign experience-based ATPL. If you don't have the hours then the JCAB won't issue your ATPL.
So;
Do you have 250 hrs PIC?
No - Do you have 70 hrs PIC
and 180 hrs PICUS (with every PICUS entry signed by the captain in your logbook)?
No - Do you have 500 hrs PICUS (with every PICUS entry signed by the captain in your logbook)?
If you don't have any of those three options then go and rent yourself a C152 in the USA and top up what you're lacking.