Significant amounts of drugs cannot move within Tokyo without Yakuza consent. Foreign and Japanese criminologists know this all too well. 2. I noticed that the (mostly, but not solely) Nigerians that always annoy me to go to "whatever" bars are gone. What does this have to do with drugs?
Statistically, in terms of usage, research indicates that Japan has a significant meth problem. Evidence that marijuana is a "gateway drug" is shakey at best and generally mocked as an outdated concept by researchers in the field.