Try this link if you go past Akihabara, and i recommend you do!

Most figure/hobby stores have at least a few TFs, but the best ones to visit are:
Yodobashi Camera.. i think it was 6th floor; Movie TF's, Encore's and Henkei.
Radio Kaikan.. this is a building housing heaps of smaller stores on different levels; all together, you could probably find most recent Japanese TF's and a few older ones.
Liberty Store #7.. must-visit store, 1st floor has got about 6 glass cabinets of TF's, mostly used, from all era's and a giant 1.5m Optimus statue!
Mandarake... ABSOLUTE must have if you're into G1, 2 full rows of glass cabinets, TF's from all era's, about 50% of it is Japanese G1. Make sure your wallet is prepared, though just seeing it is fun itself It's on the top floor, but only the right hand elevator gets to the top floor!