I am Japanese boy but not currently living in Japan.
Anyway, that's one of the hardest question.
All I can tell is meeting J-Boy somehow.
Best way is just simply go to Japan and meet the people.
Better than do nothing...
They (including myself) are so shy against foreigners this is
the major problem so if posssible you should make first
conversation and invite him for lunch or dinner just step by
This helps a lot for J-Boy.
The boy can pick up your feeling quickly as girls can do.
If you find out his feeling is tilting towards you,
There are no problem at all!!
But you have to judge the nice guy or not just
like you do in your country as usual.
Good luck \(^o^)/