30kg is ~66lbs. Paul McCartney brought 8oz of pot to Japan in 1980 and that much could have given him 7 years of jail time, had he not been an international music star. They let him out after 10 days. Cannabis laws in Japan really have not let up at all since then.
I dont think they're going to get off light with 66lbs of pot. With blatant intent to distribute, their defense of "we were told we would get a free trip to Japan if we brought these bags that we promised we wouldn't look into" is pretty damn weak.