Hmm, I know that in Korea, there are a few cafe's that foreigners hang out in, and they offer informal book exchanges.
Also try the backpackers or YHA's they usually have some form of book exchange too.
Im not sure where my friend goes in Seoul, but she has found a great book exchange. Im guessing its in the foriegner area.
Why dont you put a notice up, and start up your own book exchange? Meet monthly, over coffee or drinks, and swap books. Im sure that there would be some japanese people interested in it too.
Or go to a university that has an English Lit course, and put your notice up there.... they do a LOT of very interesting reading.