accepted drug use in japan

What's interesting, really, is that it is the brain that is addictive, not the substances at all. However, in that the OP had been asking about any 'legal' drugs in Japan, I would suggest we stick to that theme.

Coffee is among the most highly used drugs in Japan, perhaps just a little (or somewhat?) under tea. I use it often...in fact, right as I write ! And of course coffee is also legal...it is true, nevertheless, that coffee is not strong of a 'distortion' chemical mix, so few would think ill of it...Mormons, for example.

There is the ecstasy around . . . but I think it has somewhat fallen out with the law...if my understanding is correct. I'll stick with my coffee and beer...among other legal drugs.