If you want JGC, the safest way is to use an overseas address to reach Sapphire first.

When you are in Japan, apply for JAL's credit card, once you got approved, transfer your JMB to Japan, and link your JMB to your credit card.

Of course if you can maintain JMB Diamond continuously without any problem, then the above doesn't really matter.

Family JGC status is for people with JAL's credit card, I believe. So you would not get any domestic only JGC perks unless you get approved for JAL's credit card.


JALPak did mention the possible issues of incorrect address, so, at your own risk