There are few, if any, Muslims in Japan. The Japanese government makes it a point to keep them out.
But there are Koreans. Are any from North Korea?
Popular myth. They’re recruiting there as everywhere else.
Given US proclivities, some of them may be US military.
Latest figures are 125,000 foreign born Muslims residing in Japan .
But there is a Communist party in Japan. I was stationed there from '89-'92 and we had one incident, sounds similar to this, while I was there.
There was also an annual protest against the base where they would bus the protesters in, give them lunch, and they would ring the base with signs and chants. The best part is the few that would try to "CRASH" the gate. The Japanese riot police quickly addressed that nonsense in a very physical way.
I still have photos and videos of those protests somewhere.
Many of the Korean descendants of WW2 laborers are loyal to Pyongyang
However.....some years ago when the Japanese were busy building oil refineries and the like in the middle east...there were so many Japanese that the TV stations had Japanese programs on.
It seems that a number of locals learned the Japanese language and got one way tickets to Narita airport....
On arrival the spoke excellent Japanese and were not put off by the police.
Once established they brought in friends and relatives.
So there is a fairly big "underground" Japanese speaking islamic population.