Legal drugs used to be found in abundance along Bunkamura dori in Shibuya or in Kabukicho (Shinjuku). You were also able to buy peyote and magic mushrooms from head shops, that is until around the time of the World cup in 2002 when they were outlawed, supposedly because of the potential dangers of a british soccer hooligans being let loose on the streets with heads full of craziness. However, you can still occasionally run into some wannabe dealers working the streets with a card table and a case full of god knows what kind of untested chemical replicates. Care to be a lab rat anyone?
These guys weren't really keen on me snapping them, and were very quick to close the case containing their wares..