Apparently Microsoft patched it. I'm not sure where the codes will work if they will work somewhere else, which is unrealistic expectations. Codes have to be activated through Microsoft to be useable. My guess is they are checking the IP address' of the users to determine whether they are actually in Japan or not.
Basically, you're not in Japan, your code doesn't work.
That's my theory at least.
I tried this just this past Saturday and I indeed did get a code from the whole process. My tries today gave me invalid codes, all 3 times as with other users.