Legal=2C's other than 2C-B, 5-MeO-DMT, 5-MeO-AMT, San pedro cacti(Mescaline, but pretty sure refined Mescaline is illegal), 4-Aces, Salvia(inc. 20x etc. extracts), 2C-T-'s, Methylone, MBDB(and other MDMA cousins), 5-MeO-MiPT, MiPT, IAP and plenty of other obscure ones only really seen in TiHKAL etc.
Illegal=AMT, 5-MeO-DiPT(Foxy), 2C-B, Mushrooms, LSD, DMT, Cocaine, Heroin, Meth, MDA, MDMA, GHB and the other usual suspects.
The only two that have become illegal recently are AMT and 5-MeO-DiPT, but most online suppliers are saying they will sell whatever is left in their stores and then produce no more(but they are still supplying 6 months after the law was introduced...).
I would also be vary wary of pre packaged combinations of research chems and strange plant/root extracts available in most head shops, they are for inexperienced users and dont do anything compared with their chemical counterparts. As a rule, if you dont recognise the name of something, it is most likely gonna be shit. One thing that is important to note when dealing with Japanese people that take drugs is, many people arent as well informed regarding pharmacology of the drugs they are taking and the various long-term effects etc. This may be due to a limited amount of literature or something, i dunno but a few groups of people i met in my travels were perpetuating MDMA experiences and 5-MeO-DMT trips with prescription MAO-Inhibitor anti-depressants without much regard to safety and other equally risky behaviour. While obviously this is also seen in the West, the people i personally encountered doing this kind of thing were generally much less experienced with drugs than those i have seen do it in the West.
If you are gonna take drugs over there, do it at home. You wont be able to afford a cab home from a club, so you'll have to take an early morning train, and with lots of RC's pumping thru your system and the japanese people's wariness of foreigners, it will make for a nice paranoia-filled journey home.