Update the membership query with something like this:
(user.country -eq "Japan") or (user.userPrincipalName -eq "******@domain.com")
The first condition will ensure that only users with location set as Japan are members of the group, and the second one is the exception you can add for this particular user. If multiple users need to be added, you can add additional clauses. Better yet, figure out a more suitable property to use.